A chase plane is an aircraft that "chases" a test aircraft. For many years the best way to ensure the safety of an experimental aircraft during test flights was to send up an airplane that would fly alongside it and observe the flight.

This second airplane's crew would keep a constant lookout for problems with the test aircraft, and if problems did arise they would provide warnings and critical information to the test aircraft's crew and to the mission controllers on the ground.

The observation aircraft was known as a "chase plane" because it chased the test aircraft through the sky.

In the early days of USAF testing, the chase aircraft were crewed by test pilots just like the experimental planes, providing a common language and bond between test pilot and observer. The experienced pilots in the chase aircraft could guide distressed test aircraft down to safe landings when experiments went wrong.