System Wide Events: Guidance for Flight Crews

System Wide Events: Guidance for Flight Crews


This article considers the operational and airmanship factors of importance to flight crew experiencing a system-wide event (SWE) which is an event that affects a flight and a sufficiently wide area that all alternate routes and airfields briefed during pre-flight preparation have become unavailable. Ground facilities such as navigation beacons and air traffic services may also be affected.


"System wide" events present an aircraft commander with challenges that are not covered by routine contingency planning and which, if not handled well, can quickly jeopardise the safety of the aircraft.

Examples of system wide events could include:

  • Acts of War or Terrorism - For example, the closure of US airspace following the attacks of 11 September 2001, or airspace closure associated with the imposition of a no-fly zone over Libya in April 2011.
  • Natural Events - For example the closure of many airports in Japan following the earthquake and tsunami of 11 March 2011 or airspace closures over Europe on 15 April 2010 due to volcanic ash.
  • Adverse Weather Conditions - For example, widespread and unexpected closure of airports in northern Canada as a result of advection fog following changing wind conditions, or closure of airports following heavier than expected snowfall across a wide area. Tropical revolving storms can also produce widespread weather effects covering destination and nearby alternate airfields for a considerable time.

NOTE: This article does not address the more dynamic situation of operating to a destination where, at dispatch, the weather at destination and the standard diversion airfields is (legal but) hovering on limits and with the potential to improve or deteriorate; normal in-flight weather monitoring and contingency planning would then apply.

The 9/11 scenario was unusual because a government made a unilateral decision and any form of discussion was met with the threat of being shot down; the crew’s choice of diversion was taken away and aircraft went where the military could process them and determine the threat they posed. In contrast, the Japanese tsunami/nuclear reactor accident left more room for decision making on the flight deck.

A SWE will usually involve both a change of route and of the airfield of next landing. A re-route as a consequence of an SWE will not usually allow the original destination to be reached for the following reasons:

  • Even if there is no airspace closure, the change of landing airfield to one outside the areas previously briefed will involve a change of route.
  • Even if the destination airfield is unaffected, if airspace is closed over an area wide enough to exclude previously briefed en-route alternates, it is very unlikely that the original destination will still be within range.

Therefore, this article assumes that both the route and next landing airfield will change. Once on the ground, the feasibility of continuing to destination can be assessed with more complete information on the extent and expected duration of the event. Alternative means for conveying the passengers to their destination, such as ground transportation, can also be considered.

Recognition & Evaluation

Early recognition of the commencement and scale of a SWE is desirable but the event type will affect how rapidly the extent becomes evident. The start of military action may close airspace over a wide area simultaneously but it will usually be made known to ATC, through whom aircraft can be notified promptly. Adverse weather, which eventually closes airfields over a wide area, may spread relatively slowly and may come to affect what initially seems a useful landing airfield. Similarly natural disasters may have ongoing effects that spread beyond the area initially affected. Early indications may be gained through monitoring ATC communications and communications between other aircraft. If the onset of a SWE is suspected, information sources that will improve situational awareness include:

  • Air Traffic Control - ATC may be able to provide:
    • information on the nature, duration, and consequences of the event, including the impact on ATC service provision and availability of airspace and aerodromes;
    • guidance on revised routings and information regarding availability of alternate destinations.

However, be aware that the ability of ATC to provide such information and services may be affected by both the event and the sudden requirement to handle numerous re-routings and diversions, that may cause controller overload.

  • Company Flight Watch - Company flight watch centres may have information and advice to assist decision making. They may also be able to provide information on the intentions of other company aircraft and provide company preferences for the alternate destination which the crew can take into consideration in decision making.
  • Other Aircraft - especially where the ATC service has been degraded, other aircraft can be a source of useful information regarding the availability of alternate aerodromes, usable frequencies for communications etc.
  • Internet -. Some aircraft types may give access to the internet, usually as part of an in-flight entertainment system, but those sources may be of questionable reliability or contradictory; the task of gathering and assessing such information can easily become a distraction.

Although information from other aircraft can be useful, guard against allowing the assessment of another pilot to override your own judgement. The most reliable sources of information will be ATC and your operator. Advice from other ground-based agencies may be based on priorities shaped by the responsibilities of the person offering advice who may have little background in aviation.

Ensuring the safety of the flight must take precedence and the priority must be to fly and navigate the aircraft at all times: Aviate, Navigate, Communicate.

Selection of Route and Alternate

A route should be chosen that avoids the area affected by the event and offers an adequate selection of suitable alternates while retaining adequate fuel reserves. As far as possible, avoid areas with bad in-flight weather. Consider terrain clearance on revised routing (including engine out stabilising altitude requirements and drift down profiles). In areas where MSA is above 10,000’, a requirement for and the availability of supplementary oxygen may be a consideration.

Your selected landing airfield and required en-route alternates must allow for adequate fuel reserves and they must be available at the relevant ETA; if not it may be possible for this to be arranged through ATC or your operator.

Your first choice of alternative route or landing airfield may be unavailable because of saturation by other aircraft affected. Equally your selection of a near alternate when sufficient fuel is available to reach one more distant may adversely affect other flights with less reserves, for example by saturating approach slots or ground facilities such as space to park aircraft. Again, advice may be available from ATC or your operator but your first responsibility is the safety of your aircraft and its occupants.

Choosing an alternate with the facilities to handle the aircraft passengers and/or cargo, and from where it will be easier for the company to recover the aircraft and quickly restore schedules, is an important planning consideration. However, mission/commercial considerations must take second place to the need to maintain the safe conduct of the flight. Sometimes landing at a closer non-company airfield where the crew can turn around within FTL may be a better option. Ultimately, the safe conduct of the flight must always be the commander’s and crew’s priority.

Crew Resource Management

CRM aspects are the most important part of managing any departure from the intended route. Gathering, collating and evaluating the necessary information is an intensive task requiring crew collaboration. The pace of change of events may affect the performance of less experienced crewmembers. This may be mitigated by clear allocation of well-defined tasks with any new task not being allocated until previous tasks are concluded. Captain and crew should also keep in mind the impact that workload may have on their own decision making capacity.

Supernumerary or dead heading crew, if available, may be particularly useful for information gathering. In any case, at least until the necessary information has been gathered and collated and a new plan has been implemented, it is important that discussion between crew members is not allowed to compromise the operation and Sterile Flight Deck principles should be applied. Once again, flying and navigating the aircraft must be the priority and normal monitoring must be maintained.

The golden rule is one pilot must devote all their attention to minding the shop while the other(s) work(s) away at all the other stuff. However, it is imperative that the Captain holds regular updates and /or briefings so that all the crew remain in the loop.

For further information see the dedicated article on Crew Resource Management

Profile and Fuel Management

Consider adjusting the flight profile and power settings to conserve fuel, but be prepared for other traffic to constrain the choices available.

Involve the Cabin Crew

Once sufficient information is available and a course of action decided then the cabin crew should be briefed with particular attention to the remaining flight time and other factors that may influence the cabin service. Ensure that announcements to the passengers are coordinated. In some circumstances it may be advisable to curtail the serving of alcoholic drinks and this should be discussed. Duty period limits may also need to be considered, particularly if an onward flight is planned.


Once the safety of the flight is assured, the welfare of the passengers should be considered. At some point is will be necessary to inform the passengers of the situation. Choose a time when you have a clear and achievable plan for the continuing operation and liaise with the senior cabin crew because they may be bombarded with questions. If time and workload allow, try to anticipate and answer such questions in the announcement. Avoid giving information that may alarm passengers, which is better left until after the aircraft has landed. If the aircraft has access to the internet or is equipped with telephones for passenger use, remember that passengers may obtain information from external sources which they may find alarming. If in-flight announcements disagree with other sources, passengers may lose confidence in the crew.

Passengers will be anxious to complete their journey, in most cases to their original destination. The circumstances that caused the SWE may restrict onward travel for some time, in which case provision for food and accommodation will be needed. If circumstances allow, this could be a factor in the choice of landing airfield, both for the benefit of passengers and because the airline may be liable for compensation for any discomfort suffered. In rare cases, political considerations may be significant in that the country of landing may be hostile to passengers who are citizens of another country.

If a SWE occurs prior to departure, it will usually be possible to keep the passengers from boarding or to return them to the airport terminal. If this is not possible, some of the same considerations apply in providing passengers with information, food and drink.

Contingency Planning

In a changing situation, the course of action adopted by the crew may need to be revised more than once. It is important that the crew continues to think ahead and consider what they will do if, for example, the chosen alternate destination ceases to be available. The development of alternative courses of action and the critique of current plans should be encouraged.

Good planning is the foundation of good airmanship and those pilots who consider their options and constantly update them - discussing them with the rest of the crew - are always ahead of the game and less likely to get caught out.

Always keep another card up your sleeve

Do not be afraid to declare an emergency if necessary

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