Conversation so far:
who is the fastest plane in the world
The North American X-15 aircraft has the current world record for the fastest manned aircraft.
how fast can the north american x-15 go
The North American X-15's maximum speed was Mach 6.70.
who was the pilot of the north american x-15 when it hit top speed
The North American X-15 reached its maximum speed of 4,520 miles per hour in October 1967 with pilot William Pete Knight of the U.S. Air Force in control.
when was the north american x-15 introduced
The first North American X-15 flight was an unpowered glide flight by Scott Crossfield, on 8 June 1959. Crossfield also piloted the first powered flight on 17 September 1959.

Question: how about when the plane was retired
Self-contained rewrite: when was the north american x-15 retired