Definition
A button on the aircraft's transponder that, when pressed by the pilot, sends a special identification signal to air traffic control. This signal causes the aircraft's radar return on the controller's screen to flash or highlight briefly, allowing the controller to confirm exactly which target on the scope is the pilot's aircraft.
Plain English
A button on the transponder that the pilot presses when ATC asks them to. Pressing it makes their aircraft stand out on the controller's radar screen so the controller can pick them out from all the other aircraft.
Context Anchor
You encounter the ident button on the transponder control panel, especially when air traffic control asks you to confirm which radar target is yours.
Derivation
Ident' is short for 'identify.' The button does exactly that — it identifies the aircraft to the controller on request.
Why Pilots Care
Allows ATC to quickly confirm which radar target belongs to your aircraft, especially in busy airspace or when multiple targets are close together.
Intuition Check
The ident button does not announce your position by voice and does not change your assigned transponder code. It only makes your existing radar target stand out for a short time.
Example Sentence 1
When ATC said 'Cessna 172, squawk ident,' the pilot pressed the ident button on the transponder.
Example Sentence 2
The pilot pressed the ident button during the radar handoff so the new controller could locate the aircraft immediately.