With most aircraft fitted with a transponder box, here’s a list of useful ‘squawk’ transponder codes for use in certain situations.
1200 – Standard VFR code used in North America.
7000 – Standard VFR code use in Europe.
0021 – VFR code for use in Germany below 5000′.
0022 – VFR code for use in Germany above 5000′.
7500 – Hijack. Used when your aircraft is under a hijack situation.
7600 – Radio Failure. When you’re not able to transmit and/or receive communications by radio.
7700 – Emergency. Your aircraft is experiencing an emergency situation.