Definition
An autopilot mode that automatically captures and levels the aircraft at a preselected target altitude. While climbing or descending toward the selected altitude, the autopilot transitions out of the active vertical mode and smoothly arrests the vertical speed so the aircraft levels exactly at the chosen altitude, then transitions to altitude hold.
Plain English
A setting that lets the autopilot fly up or down to a chosen altitude and then level off there on its own, without the pilot having to time the level-off manually.
Context Anchor
Seen on the autopilot or flight-mode display during climbs and descents, especially as the airplane approaches the altitude set by the pilot.
Derivation
Acquire here means 'to reach and capture'. The autopilot is reaching out for the target altitude the pilot has dialed in, and then locking onto it.
Why Pilots Care
Prevents altitude overshoots or undershoots that could violate ATC clearances or create traffic conflicts.
Intuition Check
ALT ACQ does not mean the airplane is already level at the selected altitude. It means the system has started the process of capturing that altitude and leveling off.
Example Sentence 1
Passing through 8,500 feet on the way up to 10,000, the autopilot annunciator switched from VS to ALT ACQ as it began the level-off.
Example Sentence 2
During the climb the autopilot was in ALT ACQ mode and captured the cleared altitude without any intervention.