CMF Procedures

Public Benefit Flying Three-Letter Designator "CMF"
and Associated Radiotelephony Call Sign "COMPASSION"

New Procedures for Use by Authorized Groups and Their Pilots

Author: Rol Murrow, Chairman Emeritus, Air Care Alliance

Effective Date: November 4, 2019


This document discusses the Air Care Alliance's international aircraft call sign COMPASSION and its associated three-letter designator CMF, describes the procedures to be used to apply the call sign for a public benefit flying mission, and indicates when the call sign is appropriate for use.  Updates will be maintained at


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 MEDEVAC (formerly 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 in 1999 for administration to the Air Care Alliance as an organization that promotes missions conducted by pilots flying for  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 120-26M, 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, when agreements are in place with the nations where the call sign will be put into use. CMF must not be used for call signs by third party flights outside of airspace controlled by the United States except for certain CMF flights that operate in other countries that have a use agreement with the Air Care Alliance and/or the FAA.


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; transporting rescue animals or wild animals needing relocation; and in general conducting non-profit flying operations serving the public interest, especially those conducted by volunteers.


COMPASSION must not be used for routine personal, business, or commercial flights. COMPASSION must not be used for positioning or ferry flights 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. COMPASSION must not be used for flights within the United States of third party foreign registered aircraft.

Instructions for Use on Flight Plans:

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

1) Each pilot wishing to use the COMPASSION call sign:  In the block used for the aircraft call sign the pilot shall enter the ICAO Three-Letter Identifier CMF followed by the pilot's assigned call sign's numbers. If using an ADS-B transponder the identical CMF call sign must be programmed into the unit during all phases needed for the public benefit flight.

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 full name of the public benefit flying organization, and then any other remarks.

Example for pilot flying for Volunteer Fliers whose tail number is N1234:    COMPASSION N1234 VOLUNTEER FLIERS [ Using correct format for ICAO Remarks block ]

Radio Usage:

Normally pilots will identify themselves to ATC on initial call-up using the word COMPASSION and the assigned numbers as shown in the flight plan:

Example for pilot who has been assigned CMF 5678:

"City Approach, COMPASSION 5678 level at three thousand feet."


Pilots and volunteer pilot organizations are strongly cautioned NOT to use the call sign MEDEVAC (or 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 MEDEVAC (or 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, such as in order to transport a critically ill patient for immediate care.

The call sign COMPASSION is 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 MEDEVAC 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 MEDEVAC or declare an emergency if safety or medical necessity warrant its use, including changing a flight to MEDEVAC during flight if possible.  Note that most units cannot be reprogrammed in flight so if necessary then declaring an emergency may be the best option.  Ask ATC to help with your decision.

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.

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 from pilots and/or their groups 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, reasonable, 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.