Definition
A flight path on which two aircraft, if both continue without changing course, altitude, or speed, will arrive at the same point in space at the same time and collide. A key visual indicator is that the other aircraft appears to remain in a fixed spot on your windscreen, growing larger but not moving relative to your canopy or window frame.
Plain English
You and another aircraft are heading toward the same point at the same time. If neither of you changes anything, you will hit each other. The giveaway is that the other aircraft sits motionless in your window — it just gets bigger.
Context Anchor
Seen in collision avoidance discussions, especially when scanning outside for other traffic.
Derivation
Collision comes from Latin words meaning “to strike together.” Course comes from an older word meaning “a running” or “a path followed.” Together, collision course means a path that would make two moving things strike together.
Why Pilots Care
Early recognition of a collision course gives the pilot time to take evasive action and avoid a mid-air collision.
Intuition Check
Do not assume a collision course means another aircraft is simply nearby or pointed at you. The key warning sign is that it stays in about the same spot in your view while getting closer.
Example Sentence 1
The instructor pointed out a small dot that wasn't drifting across the windscreen and explained they were on a collision course with the other aircraft.
Example Sentence 2
Maintaining proper spacing in the pattern prevents entering a collision course with the aircraft ahead on downwind.