A bug is a physical or digital index marker used by pilots to set reference values on instruments like the airspeed indicator, altimeter, or heading indicator. Crews slide or dial these markers to specific target numbers during a briefing, such as rotation speed or a minimum descent altitude. They provide a quick visual cue during high-workload phases of flight, eliminating the need to memorize exact numbers.
Set the heading bug to 270 and make sure your airspeed bugs are set for a flaps-30 landing.
When a pilot says bug up, they mean accelerating to the speed indicated by the next flap retraction marker on the airspeed tape.
Also heard as
- heading bug
- speed bug
Related terms
Airspeed indicator
A flight instrument that displays the aircraft's speed relative to the surrounding air.
Artificial horizon
A primary flight instrument that shows the aircraft's pitch and roll relative to the earth's horizon.
Instrument
A device in the cockpit that displays critical flight data to the pilot.