Definition
A specified distance in nautical miles between aircraft flying in sequence on the same route, used by air traffic control to manage traffic flow into busy airspace, arrival corridors, or fixes.
Plain English
A required spacing — measured in miles — between one aircraft and the next one ahead of it on the same path. ATC uses it to keep traffic flowing in an orderly line, like cars holding a set distance apart on a single-lane road.
Context Anchor
Seen in air traffic control traffic-flow discussions, delay explanations, and aviation abbreviation lists when controllers are managing busy routes or airports.
Derivation
‘In trail’ is a long-standing aviation phrase meaning ‘following behind on the same track,’ similar to vehicles driving in a single file. ‘Miles’ here means nautical miles, the standard unit of distance in aviation. So the term simply describes how many miles one aircraft must stay behind another along the same route.
Why Pilots Care
Maintains safe intervals to prevent wake turbulence encounters and supports efficient traffic flow.
Intuition Check
MIT is not about a trail on the ground. It is about spacing between aircraft that are following the same traffic flow.
Example Sentence 1
Center advised that 15 MIT was in effect for arrivals into the New York area, so we reduced speed to build spacing.
Example Sentence 2
Approach sequencing required five miles in trail spacing for all arrivals.