Operational Air Traffic in Controlled Airspace


Operational Air Traffic (OAT) have to perform activities that are fundamentally different than those done by General Air Traffic (GAT) and are not covered by ICAO SARPs. OAT missions include air-to-air refuelling, air combat maneuvring, etc. and the aircraft involved often have supersonic capabilities.

There are two ways to ensure that (a) civil air traffic is safe and (b) operational traffic can effectively perform and train for their specific activities:

  • Segregation. This would mean that special operations are conducted in reserved airspace (e.g. TSAs). The benefits of this approach are that it is safe and simple to implement. The disadvantages are that large portions of airspace need to be reserved for just a few aircraft and restrictions of civil traffic may need to be imposed. In congested airspace such as that over the EU this could cause severe disruption of civil flights (delays and cancellations).
  • Integration. This would mean that special procedures need to be designed in order to have both OAT and GAT flights at the same time in the same airspace. As a part of the effort, the EUROAT specifications were developed in the European Union. Their main objective is to ensure that OAT traffic is able to complete their specific tasks while maintaining the desired safety levels for civil aircraft.


As far as practicable, the rules and procedures of ICAO and the provisions of EU regulations are to be used as a basis and national authorities may establish additional requirements. Therefore, aircrews need to consult the relevant documents (e.g. AIP, EUROAT chapters) of the States they intend to over-fly to ensure appropriate regulatory compliance.

The following requirements are defined in the EUROAT document:

  • General. Aircraft to be used as OAT need to be in the appropriate technical condition, and the crews must be qualified, medically fit and proficient in English.
  • Diplomatic clearance. State aircraft require a valid diplomatic clearance to cross national borders.
  • Flight Plan. A flight plan using the ICAO format must be filed before such a flight.
  • ACAS. If equipped with ACAS/TCAS, single aircraft must operate in the TA/RA mode. In a standard military formation, this must only be done by the lead aircraft.
  • Altimeter settings. Standard atmospheric pressure (1013.2 hPa) is to be used at or above the transition level (or if climbing above the transition altitude). QNH or QFE are to be used at or below the transition altitude (or when descending below the transition level).
  • Supersonic flights. These can only be conducted if permitted by the appropriate national authority upon prior individual request.

Formation Flights

Formation OAT flights are a major concern as they are usually performed by fast-moving aircraft at higher levels (compared to general aviation).

Upon each initial report on a new radio frequency, the formation leader is to indicate to ATC that the flight is a formation and the number of aircraft it consists of. Similarly to GAT, a formation flight is to be considered as a single aircraft in regard to navigation and position reporting and clearances issued by ATC. Separation within the formation is responsibility of the participants. Additionally, if the operation requires two (or more) formation flights to operate below prescribed IFR separation minima, the leaders are responsible for the safety distance between the formations.

Two types of military formations are defined. In a standard formation each element (aircraft) must remain within 1 NM horizontally and 100 ft vertically from the formation leader (as opposed to a GAT formation where the horizontal limit is 0.5 NM). Only the lead aircraft is to use the transponder as directed by ATC. Elements that are outside the horizontal and/or vertical limits are considered a non-standard formation. These flights represent an unusual aerial activity that must be pre-coordinated between the flight leader and the ATC unit concerned in due time prior departure. It is an ATC decision to approve or disapprove a non-standard formation and to determine special conditions for conducting the flight. For non-standard formations, each individual aircraft is to squawk as directed by ATC.

Related Articles

Further Reading


SKYbrary Partners:

Safety knowledge contributed by: