Transponder Codes

ATC transponder equipment is required in class A, B, and C airspaces, and in a variety of other situations. The term 'squawk' is used by ATC to instruct pilots to activate a given transponder code.

• 1200 should be squawked when flying VFR, unless otherwise instructed by ATC
• 7700 should be squawked in an urgent, distress or emergency situation
• 7600 should be squawked if two-way radio communication is lost
• 7500 should be squawked in a hijacking situation