Definition
The arrangement by air traffic control of aircraft into an orderly flow, typically for arrival, approach, or departure, by adjusting their spacing, speed, headings, or altitudes so that each aircraft fits safely into the stream of traffic.
Plain English
Putting aircraft in order. Controllers decide who goes first, second, third, and so on, and adjust each aircraft's path or speed so they all fit into a smooth, safe line.
Context Anchor
Seen in radar traffic advisory and approach control discussions, especially when several aircraft are arriving at or moving near the same airport or airspace.
Derivation
From the Latin sequi, meaning 'to follow.' A sequence is a set of things in a following order. In ATC use, it means putting aircraft in a following order behind one another.
Why Pilots Care
Correct sequencing keeps aircraft safely apart and reduces the chance of conflicts or go-arounds in busy airspace.
Intuition Check
Do not read sequencing as just “things happening in order.” In this aviation use, it means air traffic control is actively arranging aircraft into an order and spacing for traffic flow.
Example Sentence 1
Approach control was sequencing four arrivals into the Class C airport, so we were told to slow to 150 knots and turn right 20 degrees.
Example Sentence 2
During the traffic advisory the pilot learned they were number three in the landing sequencing.