Call Sign Mismatch & FAA Enforcement Action

By Peyton Metzel, PhD – Safety Committee Chair

About CMF Call Sign 
As you know, the CMF call sign is available to LifeLine Pilots as an alternative to your N-number when flying a mission carrying LifeLine Pilots passengers. Since CMF identifies you as flying a compassion mission, you may receive priority handling for routing or altitudes. This website outlines registering for a Compassion call sign, benefits of the Compassion call sign, and FAQs; it is worth reviewing.

Register for Call Sign – Air Care Alliance

Call Sign Mismatch
Importantly, the aircraft identification on your flight plan must match the flight ID entered into the transponder. For example, CMFXXXX must appear exactly in the flight plan and as the flight ID on the transponder. Most newer ADS-B transponders offer the pilot the option to change flight ID, but that function may need to be enabled by the avionics installer.

If the aircraft identification in the flight plan and the flight ID being broadcast by the transponder do not match, this error will generate a Call Sign Mismatch (CSMM), with the potential of an FAA notification letter to the pilot. 14CFR 91.217 (d)(8).

Beware Call Sign Mismatch – Air Care Alliance  

This error might arise when a pilot flies a Compassion flight outbound, and then forgets to change the transponder back to their N-number on the return or next non-compassion flight, or when a pilot files under CMF, and then forgets to set the flight ID to CMFXXX on the transponder before departing. Adding “Confirm flight ID” as a pre-departure checklist item will reduce the likelihood of CSMM. (Tip: Use a sticky note over the N-number on the panel as a reminder.)  To avoid even the exceedingly small chance of an FAA action, the pilot may file an ASRS NASA report if they determine they inadvertently had a CSMM.

ASRS – Aviation Safety Reporting System (  

Call Sign Decision
If you decide not to register for the Compassion call sign, or opt-out of using it, the pilot can use the airplane’s N-number, and enter either “Compassion Flight” or “LifeLine Pilots” in the Remarks section of the flight plan. Each is within the 16-character carry-forward limit of the Remarks section, so it should follow to subsequent controllers’ briefing strip.

The pilot should NOT use Compassion or Lifeline Pilots in any radio communications, because there is a potential risk that the controller may change the flight ID on the briefing strip, resulting in a CSMM. You can request a Public ADS-B Performance Report to validate your ADS-B performance.  

Public ADS-B Performance Report (

If you have any questions about this information, the LifeLine Pilots Safety Committee is here to assist you. 

Email the questions to and our committee chair will respond.