Key Takeaways

MAYDAY is for grave and imminent danger. Transmit MAYDAY three times, then name the station, state your callsign nature, intention, position, altitude, and POB.
PAN-PAN is for serious but not yet life-threatening situations. Same format as MAYDAY but with PAN-PAN instead.
Emergency transponder codes: 7700 (distress), 7600 (radio failure), 7500 (unlawful interference), 7000 VFR normal).
All transponder digits are 0–7 (octal). No 8s or 9s.
Radio failure in controlled airspace: set 7600, maintain last assigned altitude and heading, expect light signals at a towered field.
Radio failure in uncontrolled airspace: set 7600, proceed to destination or nearest suitable aerodrome.
Tower light signals: green (steady) = land, green (flashing) = return to circuit, red (steady) = go around, red (flashing) = divert.
Transmit blind if you believe your transmitter works but your receiver does not, or if you are out of range.
In an emergency, aviate first, navigate second, communicate third. Fly the airplane before worrying about the radio.
Remain calm, speak clearly, and be methodical. Panic transmits to ATC and can impair your judgment.