Definition
The altitude or flight level at which an aircraft is flown during the en route, level-flight portion of a flight, selected by the pilot based on regulations, terrain, weather, winds, fuel efficiency, and air traffic control assignment, and maintained between the climb and descent phases.
Plain English
The height the airplane levels off at and stays at for the main part of the trip, after climbing and before descending.
Context Anchor
You encounter this term when planning or flying the cruise phase of a flight, especially after takeoff when deciding where to level off and hold altitude.
Derivation
From the Dutch 'kruisen,' meaning to cross or sail back and forth. In aviation, 'cruise' came to mean the steady, level portion of a flight between climb and descent. 'Altitude' is the height above a reference. Together: the height held during the steady, level part of the trip.
Why Pilots Care
Proper cruise altitude selection directly impacts fuel consumption, engine wear, and adherence to assigned airspace.
Intuition Check
Cruise altitude does not mean any comfortable height you happen to choose. In aviation, it is a planned and controlled height for the steady part of the flight, and it must fit the rules, conditions, aircraft, and clearance that apply.
Example Sentence 1
After leveling off at a cruise altitude of 7,500 feet, the pilot reduced power and leaned the mixture for the long leg west.
Example Sentence 2
The flight plan listed 10,500 feet as the intended cruise altitude.