Definition
A level maintained during a significant portion of a flight, as defined by the International Civil Aviation Organization (ICAO). A 'level' in ICAO terminology is a generic term referring to the vertical position of an aircraft in flight, expressed variously as height, altitude, or flight level depending on the reference used.
Plain English
The steady height an aircraft holds for most of its flight, after climbing out and before descending to land. ICAO uses the word 'level' rather than 'altitude' so the same term works whether the height is measured from the ground, from sea level, or as a flight level.
Context Anchor
Seen in flight planning, air traffic control clearances, and international procedures that describe what height an aircraft will maintain during cruise.
Derivation
Cruising' comes from the Dutch 'kruisen,' meaning to cross or move steadily. 'Level' is used here in the ICAO sense as a neutral word covering height, altitude, and flight level all at once. This matters because ICAO rules apply worldwide, where vertical position may be reported in different ways depending on the country and phase of flight.
Why Pilots Care
Maintains safe vertical separation from other traffic and ensures compliance with airspace rules and fuel planning.
Intuition Check
Do not read “level” here as “wings level” or “not climbing or descending.” In this term, “level” means the aircraft’s selected or assigned height for a significant part of the flight.
Example Sentence 1
The flight plan filed with Eurocontrol listed FL370 as the requested cruising level.
Example Sentence 2
ICAO rules require the cruising level to be maintained until a new clearance is issued by ATC.