Summary of Emergency and Abnormal Procedures

Yes, and the danger is grave and imminent (engine fire, loss of structural integrity, imminent fuel exhaustion). → Declare MAYDAY on 121.5 MHz. Squawk 7700. Provide your nature, intention, position, altitude, POB. Repeat as needed.

Yes, and the danger is serious but not yet imminent (rough engine, partial hydraulic failure, medical emergency, fuel margin low). → Declare PAN-PAN on your current frequency (or 121.5 if you have not established contact). Squawk 7700 (note: some sources say 7700 for PAN-PAN as well). Request priority landing at nearest suitable aerodrome.

No, you have lost all radio communication. → Set squawk 7600. Maintain your last assigned altitude and heading. Do not deviate without good reason. Proceed to your destination or nearest suitable aerodrome. Expect light signals at a towered field. If you are in uncontrolled airspace, you may land at any suitable aerodrome.

Your radio is working, but you are not under control. → Squawk 7000 VFR code) or your assigned code. Proceed VFR according to your flight plan.