Definition
Small movable markers attached to the face of an instrument or control panel that a pilot positions to highlight a specific value, setting, or limit as a visual reminder during flight.
Plain English
Little pointers or tabs you slide around the edge of a dial or display to mark an important number you don't want to forget, like a target speed or altitude.
Context Anchor
Used as cockpit reminders when setting or checking planned headings, altitudes, speeds, or other important values.
Derivation
From the older English use of 'bug' to mean a small device or fitting attached to something. The term was carried into aviation because the markers are small, movable, and 'sit on' the instrument like a tiny attachment.
Why Pilots Care
They provide an immediate visual cue for critical speeds and altitudes, reducing the chance of forgetting limits and helping prevent speed or altitude deviations.
Analogy
A bug is like placing a small sticky note on a gauge, except it points directly to the value you want to remember.
Intuition Check
Bugs does not mean insects or computer problems here. In this context, bugs are cockpit markers used as reminders.
Example Sentence 1
Before takeoff, the pilot set the heading bug to the assigned departure heading so it would be easy to follow after liftoff.
Example Sentence 2
During the ILS briefing the pilot placed the altitude bug at the published decision altitude.