Definition
A specified block of time within which an aircraft is authorized to arrive at, or depart from, a particular airport, fix, or airspace boundary. The window is assigned by air traffic control or by traffic flow management to sequence aircraft, manage capacity, and meet separation requirements.
Plain English
A short time slot during which a flight is allowed to arrive or leave. If the aircraft does not make it within that slot, a new one must be assigned.
Context Anchor
Seen in flight planning, air traffic control coordination, airport scheduling, and traffic-flow programs when timing matters for arriving or departing traffic.
Derivation
The word 'window' is borrowed from everyday English, where it describes a limited opening you can pass through. Applied to time, it means a limited period during which something is allowed to happen.
Why Pilots Care
Meeting the assigned window prevents holds, delays, or missed slots that can cascade into schedule disruptions.
Intuition Check
Do not read “window” as a physical aircraft window. In this term, it means a limited block of time when an arrival or departure is expected to happen.
Example Sentence 1
The crew started engines early to make sure they would be airborne within their assigned departure window.
Example Sentence 2
We adjusted our departure time to stay inside the approved departure window.