Definition
An accident in which two aircraft strike each other while both are airborne. Most occur in clear daylight conditions, within five miles of an airport, below 3,000 feet AGL, and involve aircraft on converging flight paths where at least one pilot failed to see the other in time to avoid contact.
Plain English
Two aircraft hitting each other in flight. They almost always happen in good weather, close to airports, at low altitudes, when one or both pilots didn't spot the other aircraft soon enough to get out of the way.
Context Anchor
Seen in safety discussions about watching for other aircraft, especially near airports, in training areas, and during climbs, descents, and turns.
Derivation
“Mid-air” means occurring in the air, away from the ground. “Collision” comes from an older word meaning “to strike together,” which fits the aviation meaning: two flight paths come together when they should not.
Why Pilots Care
These events are almost always fatal and can be prevented by disciplined visual scanning and proper use of traffic advisories.
Analogy
Like two cars on the same road that never see each other until impact.
Intuition Check
Do not think of a mid-air collision only as a head-on crash between large aircraft. It can involve small aircraft and can happen any time aircraft paths meet in the air.
Example Sentence 1
A thorough visual scan of the traffic pattern is the pilot's primary defense against mid-air collisions.
Example Sentence 2
Near the airport traffic pattern, the risk of mid-air collisions rises when pilots focus too long on instruments.