Definition
A reference angle of attack used during normal cruise flight, typically marked on an angle of attack (AOA) indicator as the optimum AOA for efficient cruise performance at the aircraft's current weight and configuration.
Plain English
The wing angle the aircraft should be flown at during cruise to get the best performance. It is shown as a marker or band on the angle of attack indicator so the pilot can fly to it directly instead of chasing a specific airspeed.
Context Anchor
Seen on angle of attack indicators and in discussions of how those indicators are marked for different phases of flight.
Derivation
Alpha' is the Greek letter used in aerodynamics as the standard symbol for angle of attack. So 'Cruise Alpha' literally means 'cruise angle of attack' — the AOA value targeted while cruising.
Why Pilots Care
Operating near the manufacturer's recommended cruise alpha improves fuel efficiency, range, and engine longevity while avoiding unnecessary drag.
Grounding Statement
In cruise, the wing usually meets the air at a relatively shallow angle because the airplane is moving fast enough to make the lift it needs without a high nose attitude.
Intuition Check
Do not read Cruise Alpha as a cruise speed or an autopilot setting. It is an angle-of-attack reference for cruise flight.
Example Sentence 1
Once level at altitude, she trimmed the aircraft to cruise alpha on the AOA indicator and let the airspeed settle.
Example Sentence 2
At cruise alpha the airplane achieved its planned true airspeed with minimal fuel flow.