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Call Sign Compassion

Call Sign COMPASSION and three-letter designator CMF


Pilots flying public benefit missions and air traffic control (ATC) personnel have long recognized the need for a call sign that identifies such missions. Routine ambulatory patient transport and other public service missions conducted by volunteers usually do not warrant the priority handling provided through the use of the LIFEGUARD call sign, which is intended only for time critical medical and emergency operations such as those involving air ambulances.

The call sign COMPASSION has been developed to meet that need. Upon a formal request the call sign was assigned for administration to the Air Care Alliance as an organization that promotes missions conducted by pilots flying for all public benefit flying organizations or to similarly serve the community and public agencies.

The authority for call sign assignment and usage may be found in the US DOT Federal Aviation Administration (FAA) Advisory Circular 120-26H, especially under the criterion “… when deemed advantageous for air traffic control and operational purposes.”


COMPASSION and the Three-Letter Identifier CMF have been assigned as an International Civil Aviation Organization (ICAO) Radiotelephony Designator and Three-Letter Identifier and are thus suitable for both domestic and international operations.


COMPASSION and its associated three-letter identifier CMF are to be used to identify aircraft conducting bona fide nonprofit public benefit flying missions as from time to time may be defined in this document or revisions to it. Such missions may include the following: transporting individuals for health care, diagnostics, or treatment; transporting blood, tissues, organs, or medical supplies; transporting emergency personnel, equipment, and supplies in time of emergency or public need; performing habitat or environmental survey or other missions in support of environmental objectives; and in general conducting non-profit flying operations serving the public interest, especially those conducted by volunteers.

COMPASSION may be used during a positioning or ferry leg of flight when patients, supplies, or emergency personnel are not being transported only if such a flight leg has time constraints and there might be a need for helpful (but not priority) handling by ATC.


COMPASSION must not be used for routine personal, business, or commercial flights. COMPASSION must not be used for positioning or ferry flights when during the times of flight an actual public benefit flying mission is not being conducted; EXCEPT that it may be used when there is a demonstrable need for appropriate (but not priority) handling by ATC. Such need might be to complete in a timely fashion a subsequent public benefit flight mission. COMPASSION must not be used for flights other than those defined in this document unless permission is obtained beforehand from the Air Care Alliance or the Federal Aviation Administration. See AC 120-26H paragraph 11.a.

Instructions for Use on Flight Plans:

These instructions are demonstrated in the examples below. Pilots must file a flight plan using all normal procedures, with the following two differences:

1) In the block used for the aircraft registration (tail) number the pilot shall enter the ICAO Three-Letter Identifier CMF followed by three or four additional characters or numbers, consisting of the final three or four characters of the actual tail number of the aircraft to be used. (The block can hold a maximum of seven characters).

Normally pilots would use the last three characters of the tail number, unless it is known that another aircraft using the same number might be flying in the same area, in which case the last four characters would be used in order to avoid confusion.


 Actual Aircraft Tail number:  N7371G

    Aircraft Registration Block Entry: CMF71G  ( or: CMF371G )

        (DO NOT USE the incorrect overlong entry: CMF7371G)

2) In the REMARKS block the pilot should enter, separated by spaces, first the word COMPASSION followed by the full registration (tail) number of the aircraft, followed by the name of the public benefit flying organization (if any), and then any other remarks.



 …[Followed by any other remarks]

Radio Usage:

Normally pilots will identify themselves to ATC on initial call-up using the word COMPASSION and the chosen three or four letters from their tail number as shown in the flight plan:


 “City Approach, COMPASSION Seven One Golf level at three thousand feet.”


Pilots and volunteer pilot organizations are strongly cautioned NOT to use the call sign LIFEGUARD except for situations as defined in the Airmen’s Information Manual (see AIM 424 a or b), military AIR EVAC manuals, air traffic control handbooks, and/or other official documents. Using or requesting LIFEGUARD or the L prefix is considered to be a de facto request for priority handling, which could cause diversion of other aircraft and possibly great disruption of operations conducted by other users. It is intended to be of use when expeditious flight handling is required.

The new call sign COMPASSION is now available to identify the nature of public benefit flying missions and would normally be used for most volunteer-flown service missions.

However, should a transported person’s medical condition deteriorate in flight or other conditions apply that justify expeditious handling on a priority basis, then LIFEGUARD should be considered as likely more appropriate for use. ATC personnel can assist a pilot in making that decision, but pilots are advised to familiarize themselves with call sign usage and not to hesitate to use LIFEGUARD if safety or medical necessity warrant its use, including changing a flight to LIFEGUARD during flight if appropriate.

COMPASSION likewise has been designated to serve the public convenience, good, and necessity and we strongly encourage pilots to adopt its use for public benefit flying missions. However, some ATC personnel may be unfamiliar with the new call sign, so do be prepared to use traditional filing methods and do not be argumentative.

Also note that should pilots or organizations abuse the use of the call sign then the Air Care Alliance or the FAA can withdraw permission for its use or institute additional restrictions on its use. Likewise, should the Air Care Alliance fail to specify and authorize use of the call sign in a safe, fair, and non-discriminatory fashion then FAA may choose to revoke the authority for the use of the call sign by the Air Care Alliance and its designees.