X-15 starred David McLean, Charles Bronson,[Note 1] James Gregory and Mary Tyler Moore (in her first feature film role).

[4][Note 2]The experimental North American X-15 program at Edwards Air Force Base involves test pilots: civilian Matt Powell, Lt. Col. Lee Brandon, and Maj. Ernest Wilde.

As the test pilots prepare for the planned launch of the rocket-powered aircraft from a Boeing B-52 Stratofortress mother ship, they experience emotional and physical problems, which they share with their wives and sweethearts.

When the X-15 "flames out" on a high altitude run, after guiding the X-15 to a safe landing, saving Powell's life, Lt. Col. Brandon, flying a chase aircraft, is killed in a crash.

[7] After approaching the USAF for stock footage of the X-2 flights, the Pentagon made a recommendation that the newly introduced X-15 aircraft held out much more promise as a film subject.

[11] The film featured carefully edited NASA footage of X-15 flights intercut with original photography, with a minimum of special effects work using animation.

[Note 5][15] A archived letter from NASA Armstrong (then Dryden) to the movie producers, reviewing the script prior to production, had recommended a different scenario for a fatal X-15 accident.

That situation actually occurred several years later on X-15 Flight 3-65-97, November 15, 1967, in the rebuilt X-15-3, when pilot Mike Adams experienced a hypersonic spin on reentry.

[17] Released just as the actual rocket aircraft was making headlines in breaking speed and altitude records and reaching the upper edges of the stratosphere, X-15 was critically reviewed, receiving praise for its authenticity.

"[9] Considered a realistic look at the lives of the X-15 pilots and the efforts to fly into space, the review in The New York Times commented that it was "A surprisingly appealing and sensible low-budget picture—a semi-documentary with some harmless fictional embroidery ..."[19] Most reviews centered on the accurate portrayal of the U.S. space effort, but disparaged the tepid romantic storyline, even suggesting that the film should have been made as a documentary.