X-15

From the late 50s, this early Charles Bronson starrer dramatized the real-life development of the rocket-powered X-15 experimental aircraft, which was launched from the belly of a B-52 bomber and was flown by test pilots to high speeds and high altitude in an effort to touch the edge of space.

The X-15 was a successful part of the development program that also included precursors like the X-1 and the Stiletto, and later produced pilots for NASA and technology used in early space shuttle concepts.

I saw the film more than once on its initial run, and it seems to me this was sometimes double-billed with the somewhat similar air power goings-on of Karl Maulden's BOMBERS B-52.