FAQ (Frequently Asked Questions): 

Q. Can I use the COMPASSION (CMF) call sign?

A. YES, if your public benefit flying groups has been authorized to use the new format call signs and you have requested and been assigned a new one.  The old call signs used prior to November, 2019 must not be used after December 15, 2019.   You may request your new call sign online IF you fly for a group authorized to use it and if you follow all the guidelines  on this page. 

Note that the procedures for using it are changing so be sure to read all this information carefully.  You must be flying patients or on another official public benefit flight or exercise conducted for an ACA call sign authorized nonprofit public benefit flying group. See more detailed information in the Procedures section below. Carefully follow these procedures to avoid ATC confusion and delays!


Q. Will the COMPASSION call sign work with an ADSB-OUT transponder?

A. Yes or no, depending on your ADS-B out transponder.  You must have a model that provides for modifying and inputting a call sign appropriate for your mission since ADS-B broadcasts a call sign as programmed in an aircraft.  Many models can do this now, but this ability must enabled at an avionics shop either during installation or later.  The call sign you program into the unit must exactly match the call sign you enter on your ICAO flight plan, if you filed a plan.  The call sign MUST conform to the new ICAO International call sign requirements as detailed below.




Important Changes to CMF Call Sign COMPASSION


What's Changing and Why?

NOTICE dated November 4, 2019: 

Beginning December 15, 2019, pilots can no longer use the current method of filing CMF for use of the COMPASSION call sign.

Currently, pilots who wished to use the CMF call sign COMPASSION followed a procedure whereby the pilot enters "CMF" followed by a portion of their aircraft's tail number on their flight plan. However, that format will soon be incompatible with ADS-B out and ATC system requirements. Continued use after December 15, 2019 by a pilot could result in possible FAA violations as well as loss of any such pilot's authorization to use the COMPASSION call sign.


What You Need to Do

  1. You must STOP using the current CMF call sign process after December 15th, 2019.
  2. A new unique CMF call sign will be assigned to each pilot who flies for an authorized Volunteer Pilot Organization (VPO) and wishes to use COMPASSION. Stay tuned for further instructions from ACA and/or your Volunteer Pilot Organization on how to register for your new CMF call sign.
  3. The ACA online registration portal should be open on or before December 8, 2019.  You will be notified by your group and/or ACA when the online registration system is ready for you to request your call sign. We recommend that if you are not already on the ACA bulletin and eNewsletter list that you do so now at
  4. NOTE: ACA is sending each group an agreement that FAA requires in order for the group to be authorized to let its pilots use the new call signs. Each group must sign and return these agreements before our system will permit their pilots to register for the new call signs.

ACA's Role

As the administrator of the COMPASSION call sign, the Air Care Alliance has worked with the FAA on behalf of public benefit flying organizations and volunteer pilots to develop new unique COMPASSION call signs which will be compatible with ADS-B out requirements. ACA will on request assign these call signs to each qualified participating pilot for use on public benefit flights.

 Pilots wishing to use the COMPASSION call sign and CMF identifier MUST be registered with organizations authorized by the Air Care Alliance to use the call sign and have their new unique call signs issued to them.

Benefits of Using the COMPASSION Call Sign

Pilots are encouraged to use the COMPASSION call sign on all qualifying public benefit flights. This ICAO International call sign lets air traffic controllers know the type of flight you are conducting and may result in helpful handling by ATC.

Additionally, the new CMF assignment process gives a unique call sign that is assigned to the pilot, instead of the aircraft. This allows you to use the same call sign for multiple groups and with multiple aircraft.

The most current procedures for use of the COMPASSION call sign will be maintained on the Air Care Alliance website. Be sure to know and follow them.





















 Public Benefit Flying:
sm Call Sign and
Three-Letter Designator CMF

Call Sign Contents: Click on item to go directly to it

Procedures for Use of Call Sign "COMPASSION"

1999 Letter to Public Benefit Flying Groups and Pilots

Magazine Article in FAA's "Callback"

  Document "NEW Procedures for Use" for Call Sign COMPASSION
Information updated November 4, 2019

Expect further updated procedures for registering the new call signs soon.  Get notices by joining our bulletin and eNewletter list by using the button at the bottom of the page.

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, 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 120-26H, 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, when agreements are in place with the nations where the call sign will be put into use..


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 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 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 name of the public benefit flying organization (if any), and then any other remarks.

Example for pilot flying for Volunteer Fliers:    COMPASSION N7371G VOLUNTEER FLIERS [ Using correct format for ICAO Remarks block ]

3) If the pilot has not been assigned the new call sign:  the pilot must be sure the aircraft N-number is shown in the flight plan and in any required ADS-B out transponder.

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:


"City Approach, COMPASSION 1414 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 citically ill patient for immediate care.

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 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 eclare 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.

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 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.

  Original 1999 Letter to Public Benefit Flying Groups and Pilots

May 29, 1999

TO: Public Benefit Flying Organizations and Pilots

RE: Call Sign COMPASSION and three-letter designator CMF

Dear Friends,

On the first of this month at the Air Care Alliance 1999 national conference in Kansas City I announced that at our request the FAA had assigned an ICAO International Call Sign to the Air Care Alliance for use by all pilots and groups flying public benefit flying missions. At that time I indicated that a notice detailing the specific procedures for using the call sign, after development and a review by FAA, would be distributed to the various groups for use by the volunteers who perform the missions.

The enclosed three-page document should provide all the information your group and its pilots will need in order to begin using the call sign and associated three-letter designator. If you have any comments or questions please feel free to contact me.

In this mailing I have also included a copy of the article about the call sign that was distributed to FAA personnel in the April 13 issue of its agency newsletter, the FAA Intercom. Please note that the FAA worked hard to implement the call sign and deserves tremendous thanks for the help and advice we enjoyed.

Please freely copy these materials to your pilots and operational personnel. Note that a current version of the procedures will also be maintained on the Air Care Alliance website at and we encourage you to provide a link to it from your own site.

We at the Air Care Alliance hope that this new tool will assist you in your and your volunteers' worthy work flying to help others.

With Warm Regards,

  Rol Murrow

Rol Murrow, Chairman Emeritus
The Air Care Alliance

ENC: COMPASSION Procedures for Use; Intercom article



FAA published an informative article about the COMPASSION call sign in its magazine for FAA personnel, "Callback."


The following article was published in the April 13, 1999 FAA Intercom newsletter April and circulated to personnel at all FAA Regional Offices.

FAA Intercom

April 13, 1999

Calling All Angels

Picture: Angel Flight West is part of the Air Care Alliance that provides medical and relief-related air transport services.

It is now easier to identify angels in the air, thanks to the FAA. The agency has assigned a three-letter identifier code that can be used by pilots across the country flying as part of the Air Care Alliance, a group of non-profit charitable organizations that provide medical transport for patients.

The organization’s 4,000 members — including many FAA employees — also provide transport for tissue/organ transplants and emergency/disaster relief efforts.

The new three letter identifier — CMF — and its radiotelephony call sign, "COMPASSION," make it easier for pilots to file flight plans with the FAA, reduce potential confusion about their mission, and provide a heads-up to air traffic controllers about the type of flight they will be handling.

Rol Murrow, former chairman of Air Care Alliance, explained that some Air Care Alliance flights in the past have been mistakenly identified as "Lifeguard" flights, which receive priority handling by air traffic controllers because they involve life-and-death situations. Although some Alliance flights are flown under the "Lifeguard" identification, it is usually not necessary.

Using the CMF identifier, however, does allow Air Care Alliance pilots to request

special handling to keep patients comfortable, such as flying at lower altitudes or on routes that avoid potential turbulence.

Angel Cases, an airspace and procedures specialist in the New England Region’s Air Traffic Division, was one of the FAA leads in designating the new identifier code. Because of their mission to communities throughout the U.S., Cases expedited Air Care Alliance’s request for an identifier code. "I needed to make sure they met the requirements, and if they weren’t able to, I wanted to assist them in documenting a case for a waiver to the requirements. That way they would be able to perform their mission," Cases said.

Because of the FAA’s work on this issue, volunteer pilot organizations like Angel Flight Northeast in Andover, Mass., Wings of Mercy in Muskegan, Mich., and Angel Flight West out of Santa Monica, Calif., can now provide their missions of mercy in a clearer, safer environment.

In addition to Cases, Murrow wanted to especially thank John Elliott in the Air Traffic Operations Program and all the other FAA offices that helped with this effort. "Air Care Alliance’s mission has been supported steadfastly by officials and the rank and file of the FAA," Murrow said.

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