Definition

Military Authority Assumes Responsibility for Separation of Aircraft - Procedures between the controller and the aircraft that delegate the separation responsibility temporarily to the military authority operating the flights, thereby relieving ATC of the separation workload.

Source: ICAO Doc 10037 Global Operational Data Link (GOLD) Manual

MARSA acknowledges from the respective formation (mission) leader to the ATCO that the military participants involved in an OAT flight assume responsibility for separation (safety distance) between participating military aircraft, thus relieving the ATCO from his responsibility to ensure prescribed separation minima. The remaining responsibility of the ATCO is to provide prescribed separation between military aircraft engaged in MARSA operations and other nonparticipating IFR aircraft.

Source: EUROCONTROL EUROAT

A condition whereby the military services involved assume responsibility for separation between participating military aircraft in the ATC system. It is used only for required IFR operations which are specified in letters of agreement or other appropriate FAA or military documents.

Source: FAA JO 7110.65 ATC

Description

The safe integration of military flights is an inherent challenge associated with air traffic control. As stipulated in the Chicago convention, the ICAO SARPS do not apply to state (and hence, military) aircraft. Furthermore, certain military operations require procedures that are incompatible with the ICAO provisions (e.g. air refuelling, non-standard formations, etc.). While the reservation of special use airspace (SUA) for the purpose of performing such tasks is a possible solution, it comes at the cost of reducing the available airspace (and hence, capacity). Therefore, every effort is made to utilize SUA as a last resort. MARSA is an example of this approach. The associated procedures are result of high level coordination between the affected stakeholders (civil and military authorities). They define the responsibilities of the parties involved - civil air traffic controllers and military pilots.

MARSA is recognized as an ICAO term (see Definition section above). However, associated standard procedures have not been defined. Local implementations have been developed, e.g. in the USA, some European states, Australia, etc. While minor differences between these exist, the underlying principles are generally the same:

• MARSA is intended to facilitate the execution of specific operations that cannot be performed under the prevailing procedures. It is therefore not to be used for flight efficiency purposes (e.g. declaring MARSA in order to avoid controller intervention such as a level change or vectoring is undesirable).
• MARSA is only initiated by the military participants.
• While MARSA is in force, the civil controller is not responsible for separation provision between the participating military aircraft (this is sometimes explicitly extended to include military contract civil aircraft).
• The civil controller remains responsible for separation provision between military aircraft until MARSA is declared.
• The MARSA declaration explicitly specifies the aircraft it applies to. For example, if there are three military formations, a MARSA declaration should specify whether it applies to two of them (and to which ones) or to all three.
• The civil controller is responsible for separation provision between military aircraft and civil aircraft. Note that this responsibility may also be assumed by the military but in this case "due regard" must be stated.
• The civil controller is not responsible for verifying the appropriateness of MARSA use (e.g. they are not supposed to confirm that the military pilots are familiar with the appropriate procedures). 

It should be kept in mind that the absence of standard ICAO procedures means that any local implementation is only valid within the related airspace and variations between different countries do exist. If MARSA is not defined for a particular airspace, then it should not be used (i.e. pilots should not declare MARSA and controllers should not assume that when a pilot has declared MARSA they are not responsible for separation provision).

Related Articles

• Civil-Military Interaction in ATM
• Due Regard
• Operational Air Traffic (OAT)
• State Aircraft and Formation Flights - Separation Minima
• Operational Air Traffic in Controlled Airspace

Further Reading

• Specifications for harmonized Rules for OAT under IFR inside ECAC controlled Airspace (EUROAT)
• FAA JO 7110.65 ATC
• Flight information handbook Australia