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Sector Over-Deliveries Due to Non-Adherence/Response

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Detailed Responses

Aircraft Operator Organizations and Associations (AO)

AO 1

How does non-adherence of EOBT/CTOT, requested level, or change of routings affect your operations?

  • If talking of CTOT, it is always a delay, so it affects negatively; only when a ready message is considered, the damage is lower.
  • When talking of EOBT, if we get off-blocks earlier, better for us and for our customers, but we never get more than 5 or 10 minutes. If we are ready earlier than that, they force us to change our FPL. If we get later - same as “a”.
  • As for the requested FL, we always benefit, because the fuel consumption is lower. It uses to happen that a lower number of passengers -or cargo- show up, so we are able to climb higher. If we adhere to the original FL in the FPL, consumption and emissions are higher.
  • Change of routings. Sometimes is for saturation; in this case the new route uses to be longer, so it is worst. If the rerouting is improvised in real-time (via direct instead of angled), again, is better for us, for fuel consumption. But in this case, there is no chance to get a direct to if control doesn’t agree or is saturated.

What are the possible reasons (root causes) of non-adherence?

  • Other than the self-explaining ones (demanding it for fuel savings), I can only think of case “b”. These delays answer to several reasons (passengers that are late, airport security personnel not enough for the demand, congestion, weather problems, you name it…) In our case, very seldom this is due to lack of flight or cabin crewmembers, late show, late manage, maintenance or similar.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

  • Better software, that would allow Flow control to better manage the sequence of the flights, whether from the time a FPL or a RFPL is known or presented, or whether in real time, as it goes. Flights should not be tracked the same way they were tracked 50 years ago, via VOR’s or NDB’s, through airways… software and powerful computers allow to route most of the flights direct from take-off to destination finals, sequencing the flights with only minor deviations. Sweden is beginning to test this in a certain area over a certain altitude, but it should be tried deeper.
  • To try to solve problems related in “e)”, the crisis and the low cost business has taken us into a situation where personnel is lacking everywhere, so it would be difficult to ask the airport to bring more security people, to put more desks, to install better NAVAIDS, to bring more controllers, and so on…

AO 2

This is a serious issue. As far as I am aware, nowhere does it say that the pilots have to adhere to their filed flight level. In flight we assess the aircraft mass, the winds (and turbulence of course) and ask for different levels if appropriate - either up or down. Furthermore, direct routings happen all the time - on every flight. I doubt that there is any operator anywhere which doesn't use them. So, what's worrying is that Central Flow Management Unit (CFMU) seems to think these things are happening when they very clearly are not.

AO 3

These questions are being discussed as well for many years in different working groups (e.g. in the EUR AOG group). From our side we can say that AO 3 is doing the utmost to adhere to filed routing and levels, CTOTS / EOBTs, etc. Just to give some examples:

  • Dispatchers are updating the EOBT of the AFP based on the standing rules
  • Cockpit crews have updated flight plans available. The AFP is corresponding to the OFP.
  • In case of ad-hoc re-routings due to slot, the cockpit crews gets updated documents via Aircraft Communications, Addressing and Reporting System
  • Cockpit crews are informed by dispatch in case a flight is re-filed on a different level to avoid a restriction

So from our side I feel that we do everything to avoid the mentioned over deliveries.

AO 4

How does non-adherence of EOBT/CTOT, requested level, or change of routings affect your operations?

If in conflict of traffic it will indeed raise a serious safety concern. With Reduced Vertical Separation Minima (RVSM) we do not need TCAS RA alters due to traffic not adhering to FL / routing, unless approved by ATC in which case there should not be any conflicting traffic!

What are the possible reasons (root causes) of non-adherence?

Most probably fatigue!? I.e. if a [flight number] or other traffic leaving [country] taking off in [city] between 16:00 - 18:00Z, arriving in [destination] between 04:00 - 06:00Z! Long over night flights arriving in [destination] early in the morning. If just taken off in [region] then most probably some kind of distraction?

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

I suppose there is very little the ATM environment can do and as such it would be up to the Operators to ensure compliance! I.e. Fatigue Management Training / CRM Situational awareness / control reminders / training / vigilance and last of all - effective monitoring by the Pilot Monitoring!

AO 5

How does non-adherence of EOBT/CTOT, requested level, or change of routeings affect your operations?

Not noticeable.

What are the possible reasons (root causes) of non-adherence?

Commercial pressure?

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

When it occurs crews get called by Flt Ops Management, followed by a Flight Crew Notice to alert crews to the instances were it’s not acceptable Note: We’re a night operator.

AO 6

We stress to all our flight crew that on-time performance and fuel burn minimisation are second only to safety and they take this one step further and recognise that getting people to their destination early is even better than getting them there on time! Both long haul and short haul crews recognise these principles and try hard to help in context. They will always try for direct routings and will happily accept the best they can get out if the EOBT/CTOT ‘system’. One additional pressure which our own crews do not face but which seems to be a significant influence for short haul crews in some other Operators is that the ‘push’ to get to destination ahead of schedule can be encouraged by the knowledge that the scheduled turn round time at destination is barely sufficient for the essentials let alone a chat with the cabin crew and a crew meal eaten in the cabin.

Requests for cruise flight levels different to the RPL are likely to be a result of one or more of:

  • passenger comfort considerations including CAT and (for short haul) layer cloud tops avoidance
  • a desire to fly the optimum profile for actual aircraft weight rather than the assumed weight used to determine the RPL cruise level
  • detailed differences between aircraft type variant performance versus the variant used to determine RPL cruise level
  • the operation of a particular flight under an RPL where an aircraft type change has not been amended

As an Operator, we are not surprised to learn that deviations from the traffic plan perpetrated by controllers motivated to function at their personal optimum and encouraged by flight crews who willingly accept improvements to their journey apparently create systemic inefficiency. We can see that if the system is operated properly all operators will benefit. But we live in the real world where, if we ask our own crew to be less tenacious in their pursuit if our objectives (except for strictly tactical avoidance of discomforting en route turbulence), we risk losing out to other operators who might be less principled in their outlook.

So the best suggestions we have are:

  • First make it possible to file as direct a routing as possible for all scheduled operations
  • Only once that is done, stop deviations from RPL routings, levels and cruise speeds unless there is either an aircraft safety issue (e.g severe airframe icing) or a genuine pax comfort problem with in-cloud turbulence or CAT
  • Make it a requirement that all flight crew requesting a deviation give adequate descriptions of the actual or anticipated weather circumstances which have led to their request, especially in the case of CAT or layer cloud tops turbulence
  • Ensure that all ACCs can display (and adjust) weather returns on their radar screen when appropriate so that the potential impact of significant convective build ups can be taken into account proactively before the requests for deviation start coming in.

AO 7

There are two types of flight notification in common use by airlines. One is Flight Plan (FPL) and the other Repetitive Flight Plan (RPL). FPL is a calculated plan and RPL is, in effect, a seasonal plan.To plan an RPL for a season is a useful tool for the airlines where there is no route selection choice. However, the usefulness for ATC decreases once flights are conducted outside of enforced FL profiles. RPLs are prepared up to six months ahead of a flight and are based upon a statistical wind for the FL profile. That’s the first inaccuracy introduced where it is not possible to determine in advance what the wind component will be for a particular flight in the future. If winds are much stronger than statistical, an automated flight planning system may consider a lower level than that originally notified. Likewise, the second inaccuracy would be payload and the use of a statistic load in preparing the RPL FL profile. On the day differences in payload may result in a completely different optimum FL from that planned in the RPL. There are other reasons, such as turbulence, why a crew may ask for a lower FL than planned. Turning to RPL times, statistical winds are used here for RPL profiling and times. On longer RPL segments where no route choice exists, a computed profile on the day may well differ from statistical, so the flight times are out. Do all ATC systems take winds into account when determining sector counts? Calculated FPLs generally have better more accurate profiles as the computation is performed hours before a flight when there is a good estimate of payload available. Timings for individual sectors are not computed by an airline but the flight is planned according to the latest wind forecast available. If ATC do not use wind data then the sector timings will be inaccurate. Other reasons for discrepancies are the high cost of fuel and the use of a variable Cost Index. Real cost index varies on a per flight basis, so any RPLs may not reflect this. A crew asking for a FL above, on a level capped flight, can also cause a sector overload, if that level above is in a different sector later in the flight. At the moment, there is no mechanism in place to identify a level capped flight to both crews and ATC. The good news is we are moving away from RPLs and introducing a new system that will provide better optimal profiling. Not every airline can afford to move away from RPLs. In the future, I would suggest sector times on an enhanced ATC Plan, but for that to be provided, standard sector information needs to be published in AIPs. As well a standardised ATC system, to better predict real-time sector overloads that are available to individual controllers before divergence from planned FL is allowed.

AO 8

This is an interesting issue. But I think that as long as RPLs are in use, this will remain. Has there been any survey on how much deviation there is among operators using RPLs and those not using them? When filing an RPL you make a plan based on statistics, and then you operate under actual circumstances. This will probably lead to that 15-50% of the flights will change their flight levels / times in order to be fuel efficient = environmentally friendly.

So I would say that the Free Route Airspace should be implemented as far as possible not only for scheduled airlines, but for all. Then try to get away from the static RPLs. After that we can explain to crew the reason why they should stick to their planned trajectory as far as possible. There will always be a minor need for deviations due to WX etc.

AO 9

How does non-adherence of EOBT/CTOT, requested level, or change of routeings affect your operations?

As EOBT/CTOT usually pose operational restrictions on a flight

  • Delays may be reduced or avoided by early take offs. Short ground times put a strong pressure on pilots to fly in time as more than one flight is affected by delays.
  • Requesting higher levels or change of routes reduces fuel consumption and may save flight time
  • If an EOBT/CTOT could not be made in time disregarding it may save a huge amount of delay (new EOBT/CTOT will be much worse)

What are the possible reasons (root causes) of non-adherence?

  • Pilots request early take offs and optimum flight level rather than the requested level as they expect ATC to have the authority and judgement weather to divert from the EOBT/CTOT or not.
  • Pilots can usually not judge the effects of change of routeings on EOBT/CTOT requirements
  • Non-adherence of EOBT/CTOT has usually no negative consequences for the crews
  • It seems that some countries out of Europe do not take into account European EOBT/CTOT requirements for start-up/take-off clearances.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

  • ATC should avoid clearances opposite to EOBT/CTOT requirements (e.g. take off clearances, route or level changes)
  • Pilots need more information about consequences of change of routeings on EOBT/CTOT requirements
  • Pilots need more information about possible consequences of non-adherence of EOBT/CTOT (e.g. in flight holding).

AO 10

I would like to take this opportunity to underline one of the simplest ways to solve some of the problem - radar. This issue has been already brought to Eurocontrol attention in past.

You have the most reliable and real time tool to trace, control and predict flight time between reporting points, furthermore in many occasions the route is changed in agreement with ANS, and under ATC control, hence, at least, as far as the predictability is concern the radar is still not used with the extent of its full potentiality.

Another component which the colleagues will highlight as one of the reasons for non-compliance is the wind component - another component which can be monitored by the radar trough the aircraft position.

We would like to stimulate all stakeholders in a more active participation in the aviation target -punctuality.

Air Navigation Service Providers (ANSP)


How does non-adherence of EOBT/CTOT, requested level, or change of routeings affect your operations?

Non-adherence in general definitely affects the workload for the controller and the unit, and it might affect safety, too. In general non-adherence to EOBT has little impact on our operations. Such cases will often balance each other, as some will depart early, some late. Non adherence to CTOT will of course have an impact on our own regulations. We have had cases of over-delivery especially on [airport] arrival regulations, but also this has a tendency to balance each other. EOBT/CTOT does not seem to be a big issue at the moment in [ANSP], but (late) changes and requirements for deviation from requested flight levels and routings in filed flight plan happen quite often. Peak-periods with high workload combined with aircraft requesting changes from their filed flight plan (level, routing etc), is a safety issue. Pilots ask for direct routings, which might seem like a good idea for the ATCO at the time given, but the consequences to follow often appear at the adjacent sector or area control. Non adherence to RFL has very little (if any) impact, as all our ACC-sectors cover controlled airspace from bottom to top. Some airline companies are believed to deliberately plan on making such changes - they file a routing/level which will give them a preferred slot-time and later they put on a request for change in routing/level which would not have given them a convenient slot if filed in the first place. In addition to this, some companies declare "low on fuel and requests priority " suspicious often to get first in line for the approach. We do not know for sure if such actions are deliberate or not. What are the possible reasons (root causes) of non-adherence? For EOBT/CTOT changes: a tight time company schedule, challenges with ground operations/turnover process at the airport, weather (during winter) , traffic density on ground, ATC/ATCO For level changes: weather, change in aircraft weight/loading, ATC/ ATCO For change of routings: time schedule, to save time and fuel, weather, ATC/ ATCO One of the root causes is ignorance amongst TWR controllers and local AO personnel. They are normally not well educated to see the consequences of non adherence.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

Information to ATC and to AO about the consequences, the extra workload and possible safety issue (late) changes create. A better and compulsory ATFCM-education of TWR and AO personnel.


Regarding [airport], I can confirm that frequently the capacities announced to Brussels are not always respected resulting in a higher workload for the ATCO's at [airport] TWR/APP. On the other hand, it's sometimes (especially during winter time - charters/weather/de-icing) hard to strictly respect the CTOT's for departures from [airport], working with a single runway, and so other centres get the same congestion problems than we have. Pilots or ATCO's tend also to ask/offer as much as possible direct routing for ecological and economical reasons but also to provide an expeditious flow of air traffic, and as said in the message below this also has a big impact on capacities. The last point is maybe that pilots getting bad slots will have the tendency to fly faster and often ask for short cut to bring back the delay and this also contributes to unexpected overload of ATS sectors.

Toolkit: honestly I have no good solutions but, CTOT's remain theoretical, depending of wind differences en-route, selected speed set by pilots, etc. With the actual conjuncture, I'm not sure asking ATCO's or companies to strictly respect the RFL or FPL route would be acceptable but in order to solve the capacities problems it could be one solution.


The issue of over-delivery has been a constant within ATC ever since the creation of CFMU. From an initial reluctance by ATCOs (supported by many pilots!) to allow anybody outside their airspace to govern their departure times through CTOTs, to the present-day situation where every controller likes to feel the protection offered by ATFCM measures, and more specifically regulations. Tactical loads are not always properly understood during normal operations, and too often acting belatedly results in actual traffic overloads which result in safety concerns, in spite of the fact that tactical control is supposed to be able to safely mitigate such risks, but probably without the desired efficiency. The way traffic load is counted tactically is also changing in order to dismiss some of today’s problems.

We agree that over-deliveries are a safety concern, produced at a stage in which safety management can do little to mitigate or avoid it happening. ATC Operations, meaning the ATS Division mostly, must take the risk of over-deliveries on board from the start through proper planning and supervision, as they are the ones interacting and coordinating pre-tactically and tactically with CFMU.

Basically, over-deliveries arise from early operational action(s) by any different actors where only tactical remedial solutions can eliminate or reduce the potential risk. This potential risk is always that of "ATCOs excessive workload" and any event derived from it.

Over-deliveries are a safety concern, in the same way as go-arounds: they are usually the result of some flawed previous actions. Nevertheless, these are of such a varied nature in their origin, due to the enormous amount of factors influencing real time traffic flow, that as a safety manager it is very difficult to investigate and properly assess the decisions and actions taken by all parties in the operation: ATC, flight crews, FMPs, Central Flow Management Unit (CFMU), AO OPS and Flight Dispatch, MET constraints, shortcuts, etc. It follows that mainly general safety studies can be undertaken where average conditions in which over-deliveries take place are established, and possibly also, the trends from which to take further action. From the safety management point of view I think we can assist by anticipating or alerting the operational management and ATCOs towards taking timely tactical action, and the risks involved when not doing so

On tactical bases, three main actors intervene:

  • AOs
  • ATC
  • CFMU-FMP coordination

How does non-adherence of EOBT/CTOT, requested level, change of route affect our ops? AOs: AOs here has to do with the flight planning offices. Keeping ghost flights in the FMP´s TRAFFIC LOAD, or duplicate ones, create a great distortion on the figures upon which decisions of whether to regulate or not are taken. Possibly this is kept now to a minimum compared to the past, but it is absolutely essential that AOs cancel or send DLA messages as their schedules get updated. Reading the log books from Towers there is still a small but relatively significant number of duplicate or very similar flight plans belonging to a same aircraft. Also, we are used to see that an aircraft may have left within its CTOT or not, but that crews take pride in announcing that arrival time was actually earlier than scheduled, thus entering approach sectors probably well before expected. ATC: Same as above, Some smaller remote units may still feel that relatively short-haul flights, specially when there are few aircraft on the ground, do not deserve to stay there until they reach their CTOT. Bigger units work with the pressure of keeping a high number of aircraft coming in and taking-off from already saturated airports, and CTOT compliance may come second as a priority against letting the flight leave. There is a general impression that once the aircraft is airborne, even behind its CTOT, someone will make up for the lost time and shortcut him to comply in the end with expected the arrival time at destination. And it is often the case. CFMU-FMP coordination: Load figures vary too rapidly in the FMP sector screens, but by then it is too late for any coordination, except if the over-delivery extends itself for more than 3-4 hours, in which case a restrictive regulation would have to be put in place.

What are the possible reasons for non-adherence?


  • Tweaking with flight level information as to avoid a restricted sector, then, once in the restricted sector, asking for higher.
  • Filing for a non-restricted airport with a restricted one as an alternative, then requesting to land at alternate when en-route
  • No updating of flight plan changes, including EOBT and FL/Route and changes in FL or speed along the route.
  • MTOW and fuel quantity non consistent with real flight plan, higher GS, winds, etc.
  • Asking for shortcuts
  • Commercially-driven and unrealistic turnaround times at airports


  • Granting crew’s requests for change of FL or destination against what was originally scheduled on the flight plan, and even if the aircraft is taken through regulated sectors
  • Granting shortcuts (we love it!) but I refer to Bert Ruitenberg´s article on Hindsight "Are We Too Good?"
  • Disbelief that letting an aircraft go ahead or after EOBT/CTOT toleration times will have any effect hundreds of miles away
  • Impression that Load figures vary too much, too often
  • Intentional, biased traffic count periods
  • unrealistic declared sector capacity
  • Operational constraints, impossible to avoid (runway changes, airspace closure, thunderstorms, runway temporary non availability, etc.)

CFMU-FMP coordination:

  • unrealistic and/or inadequate requests by FMPs for the application of traffic exemption measures
  • wrongly defined traffic volumes
  • inadequate sector design, not capturing all aircraft desired
  • Constant changes in taxi time



  • Avoid flight plan duplication
  • Strict adherence to CTOT
  • Submit realistic FL and speed intentions
  • Avoid requesting to enter regulated airspace once airborne, unless originally scheduled through it
  • Reduced corporate pressure (turnaround times)


  • Education on the concepts of "over-delivery" and "workload" during their basic and unit training on ATFCM/Safety issues
  • Routes should be gradually redesigned according to AOs preferences
  • Analyze adjacent sectors impact with an appropriate tool at workstation level
  • En-route ATC instructions to deviate from flight plan in order to avoid sector congestion
  • Timely and increased coordination with adjacent sectors
  • Training of traffic load balance between sectors when an impending overdelivery is anticipated
  • Teamwork

CFMU-FMP coordination

  • Revision of wrongly defined traffic volumes
  • Revision of inadequate sector design, not capturing all aircraft
  • Regular supervision of declared sector capacity adequacy
  • CDM for situations where an over-delivery might extend itself in time


Tactical changes to any part of the flight plan cost time to the controller; i.e. either capacity or safety or both is compromised in order to provide 'improved quality of service' as most ATCOs would understand it. From a business point of view, the reduction of capacity far outweighs the ad- hoc improvements at individual flight level. We estimate approximately 5-10% of capacity is 'reserved' to take care of all non-adherence issues, such as the above tactical events, as well as pre-tactical and tactical time non-adherence. At [ACC], we work upon a hypothesis that 5-10% is the complete capacity gap (i.e. is the current cost-optimum ratio of delay and demand versus staff resourcing).

This argument seems to be borne out by the 2008 and 2009 traffic patterns; a reduction of 8% is equivalent to achieving zero delay. Accepting then this hypothesis for the moment, the difference in indirect cost to the customer in case of a more compliant/reliable system of ATFCM is worth 700,000 minutes at 65 euros per minute, therefore roughly in the order of 45 million euros.

The cost benefit argument for appropriate investment in achieving this performance improvement would, at first sight, seem highly attractive, particularly at pan-European level. The safety benefits cannot be calculated, but may be considered equally rewarding.

We strongly support any efforts by CFMU and others to address these issues, including the application of regulation to deter inappropriate practices.

How does non-adherence of EOBT/CTOT, requested level, or change of routeings affect your operations?

Non-adherence directly affects capacity, can and does create overloads and in the end regulations and wasted airspace capacity.The network has allocated a slot based on route and RFL etc, the network relies on compliance.

What are the possible reasons for non-adherence?

ATC and AOs offering and/or requesting level change, direct routeings plus lack of airport respect for slot compliance.

Recommendations or proposed solutions

The solution is slot time and profile adherence. To achieve this you need the agreement/discipline of all participants - AO,s ATC ATFM - in other words strong CDM. Failure to adherence requires a form of regulatory firmness, possibly a punitive approach to regular offenders.


How does non-adherence of EOBT/CTOT, requested level, or change of routeings affect your operations?

It is especially the upper high sectors/en-route sectors in [ACC] which are affected by the non-adherence. Often flights come in a higher level than planned, earlier or later than expected or in another sector and the configuration chosen pre-tactical shows not to be the right one. Capacity is wasted in some sectors while other sectors are overloaded. Especially when the manning is tight it is not always possible to change configuration immediately or open even more sectors.

What are the possible reasons (root causes) of non-adherence?

Off course there are all the changes being made for separation or weather purposes both to route and flight level, but when not taking them into account it is mainly because of traditionally thinking. In the early days of ATM the route network wasn’t optimum for flight planning and the flight planning tools weren’t able to give optimum routes. Therefore the controllers and pilots often arranged the optimum flight tactical. It was possible because the congestion of traffic wasn’t as intense as it is today. Unfortunately old working methods are difficult to change, and to some extend the controllers and the pilots still think they know best and therefore choose to fly the most optimum flight for them even though the flight plan says otherwise. It is still not widely accepted that the flight planning tools of today actually can predict the most optimum flight plan within the known constraints of the Airspace. Also there is a big difference in the flight planning tools the AOs use and not all have the most sophisticated ones, which still leaves the controllers and pilots in situations where they know best. In the operational part of ATM there’s still a great lack of understanding for the network effect of ones actions and decisions between the operational staff (both ATCO’s and pilots), and as well some AO’s seem to prioritise the need for a better flight planning tool rather low and instead count on getting the optimum route and level from ATC.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

Everybody in the network has to be made aware of the problems. All stakeholders have to agree on a common solution and approach and ensure that this is implemented through out their own organisations all the way “down” to the flight planner, ATCOs and pilots. Our route network should be updated to what is actually flown so direct routes become plan able. This will give a more correct predict of the flight and ensure that only the capacity in the actual effected sectors are being used.


There are figures published for CTOT compliance although the accuracy has some questions to answer. EOBT data is also available. In general both need to be tackled for non-compliance. The use of incorrect data when using predictive tools results in ATFM measures where the traffic is not turning up and the regulation or scenario having no use other than to frustrate the operators and sow doubt about the value of such tools with operational staff. The latter is further compounded when indications show that demand is such that ATFM measures are not necessary and an overload (or potential overload) situation occurs. Operational staff often blame the tool when poor EOBT and CTOT management is the issue. AOs failure to update EOBTs is a fundamental cause compounded by ATC failure to manage both the operators and the CTOT compliance.

Safety data from the last 3 years shows;

  • 4 Overloads and 7 safety observations have failure to update EOBT as a causal factor
  • 2 Overloads and 1 safety observation has failure to comply with CTOT as a causal factor

There is an issue with archive data which means it cannot be guaranteed accurate as far as EOBT compliance is concerned therefore it is very difficult to be absolutely certain that non-compliance was an issue.

The issue of level compliance requires direct instructions to ATCOs to give the flight its filed level and not ask what it would like. ATCOs need to ‘act local but think global’ of the consequences of taking flights at levels different to that on the flight plan.

We need AOs to move away from the ‘Bulk File’ and use flight planning tools.

Regarding climbing aircraft to levels other than those flight planned it is difficult to determine how many overloads / reports this has featured in as there is not an exclusive causal factor for which to search. A best guess is around 4 over the last 3 years.

There appears to be an issue with operator flight planning. Experience and reports from the ops room indicates that many flights request a level other than that which is flight planned. If controllers do not ask for the requested level this can cause problems when the level is lower than planned as the accepting sector may not have capacity at that level or a late revision may need to be made to onward sectors. Conversely if a higher than planned level is requested many (but not all) controllers offer this level if it is available in their sector. Some operators are worse than others in this respect.

A relevant recent example would be a flight from [region] to [country] which had filed to cruise at FL370 and then descend to FL300 before the boundary of a sector which had regulation imposed. The flight plan then intended the aircraft to climb back to FL370 when clear of the regulated sector. The regulation concerned was invisible to the sector controllers. As a result the aircraft was not descended and was offered to and accepted by the regulated sector at FL370. The supervisor was surprised by how busy the sector had become and found on further investigation this flights profile, which had not been “planned” to be in his sector.


How does non-adherence of EOBT/CTOT, requested level, or change of routeings affect your operations?

Regularly we have over deliveries but this concerns much more the arrivals than the over-flights. This over-deliveries might go up to 10-15% more than the requested capacity. The consequence of this will result in aircraft entering the holding.

What are the possible reasons (root causes) of non-adherence?

  • Aerodrome slot not respected (aircraft taking - off before or after the allocated slot, sometimes only 1 minute but it is already too much) (mainly).
  • Direct routings?
  • CFMU allowing about 10% more than the requested capacity?

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

Aerodrome shall stick to the CTOT.


How does non-adherence of EOBT/CTOT, requested level, or change of routings affect your operations?

Non-adherence of EOBT/CTOT, requested level, or change of routeings may lead to situation when more aircraft than planned enter protected sectors, exceeding their capacities. Capacities of sectors have been designed on basis of the best experience how many aircraft can be handled without controllers were overloaded. With non-adherence to the planned flight path and timing we loose predictability of the traffic demand.

CTOT: The non-adherence of CTOT resulted in the complaints of CFMU two years ago. We had had about 21% aircraft departing out of the CTOT.

Requested level: It’s not so big problem in our FIR. There are a lot of aircraft climbing or descending within our FIR [list of cities] so the amount of aircraft coming in different level is low not affecting strongly the sector capacity. Moreover most of entry/exit FIR points have a clearly defined FL (LOA) for hand-over procedure

Change of routings: It’s a common thing in our FIR to instruct pilots to fly DCT anywhere. About 70% of DEP from [airport] do not follow SID. Such aircraft can arrive to next sector earlier and increase ATCO’s workload but I do not know exactly if this is the main problem. Worse problem is if sector/airport capacity is calculated for 60 minutes long window instead of 10 minutes. In consequence it means you have a declared capacity 40 movements per hour but aircraft arrive in waves (surge) = 10 during the first 30 minutes (you are bored), 30 during the next half an hour (workload is too high).

What are the possible reasons (root causes) of non-adherence?

There is common practice that it is normal to change planned routes and levels without necessary operational or traffic reason, regardless whether flow management is in progress. On the other hand we have an experience that pilots and controllers are in compliance with EOBT/CTOT.

CTOT: The reason is very simple - we use a single RWY for both ARR and DEP. So if there are a few aircraft waiting for departure at holding point controller has to take advantage of every available gap between two arrivals. So ATCO has to decide whether he allows aircraft to depart before the CTOT window or not (to keep aircraft waiting for next gap and causing a delay of the other ones).

Requested level: Sometimes airliner (private, business) tries to avoid a delay (CTOT) due to the reduction of a sector/airport capacity. So in FPL there is written a higher requested FL (not subject to restriction = different sectors) than really flown (given by aircraft performance criteria).

Change of routings: Why to fly ‘zigzag’ via standard route if one can fly DCT to exit FIR point saving time and fuel? And pilots are grateful. The shorter time you have aircraft on frequency the better. Every aircraft leaving your sector is good aircraft.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

CTOT: After the CFMU complaint we began to monitor the number of aircraft departing before or after the CTOT window for every month. Controllers are conscious of that and the main goal of this activity has been to reduce the non-adherence of CTOT. Now we have had about 12% DEP flying out of the CTOT - the necessary amount given operational conditions.

Requested level: May be the correlation between aircraft type and requested FL in FPL?

Change of routings: Redesign the airspace - straighten the routes. To calculate the sector capacity for 10 minutes long window or less. It should be established rule that when flow management is in progress, controllers should initiate a change in the planned route or flight level only in order to ensure separation or spacing. Controller may also clear a change of planned level or route at any time on pilot’s request. Pilot of aircraft which is subject to ATFM measures should be aware that he/she should request a change of planned level or route only when it is necessary for safety of the flight e.g. due to turbulence, icing, thunderstorm, lack of fuel etc. Optimisation of the flight path shouldn’t be considered as essential reason in this case. Fuel saving and environmental benefits resulting from the optimised flight path may be significantly devalued by later delay of this aircraft or other aircraft on route due to non-adherence of ATFM principles. There should be some pressure developed on the AOs which do not plan their flights flexibly in accordance with the actual state of different circumstances (i.e. number of passengers, weather, fuel etc.) and the AOs have been proved cheating the ATFM system should be penalised. Actually, some of these issues and proposals are already described in the brochure "Flight Plan and ATFCM Adherence ..." issued by Eurocontrol. We agree with all what has been said in the document but recommended actions are basically in place already for a long time and seem to be not enough.


How does non-adherence of EOBT/CTOT, requested level or change of rerouting affect your operations?

No significant impact due to low-medium complexity traffic in [name] FIR.

What are the possible reasons (root causes) of non-adherence?

Non-adherence CTOT: works in progress on airfield; lack of ATC planning & coordination; pressure on pilots / AO Non Adherence to EOBT: AOs knowledge and awareness; airport delays; inability of ATC to clearly manage EOBT compliance.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

  • FSA/CPR transmission by all states
  • Ongoing awareness to all stakeholders especially on FPL requirements
  • EOBT: possible introduction of a CFMU message like SAM to regulate EOBT compliance.


How does non-adherence of EOBT/CTOT, requested level, or change of routings affect your operations?

All this result it over-delivery of the sector and not expected high workload for our personnel.

What are the possible reasons (root causes) of non-adherence?

The basic reason is that the ATCO at previous sectors / FIRs is not well aware of the restriction applicable to the flight concerned (poor presentation if that information to him) and in case of need (ATC side - separation or LoA condition) or request (A/C side - SIG WX or performance ) there is not planned / expected FL change resulting to additional aircraft enters not planned sector. The network effect is unknown or underestimated to ATCO during the decision phase.

What are your recommendations or proposed solutions to improve adherence and avoid re-occurrence?

More precise tracking and ANSP informing of the airlines / operators not following FPL route or FL allocation or Europe wide information campaign would help.