An unnamed extra in this movie, Virgil Ivan "Gus" Grissom, was later selected as one of the original NASA Project Mercury astronauts. Grissom died on January 27, 1967, during a pre-launch test for the Apollo 1 mission at Cape Kennedy, Florida, along with his fellow astronauts Ed White and Roger B. Chaffee.
This is one of the best examples out of Hollywood where the technical advisor got all the actors to properly render military salutes. In virtually every case the junior officer/cadet saluted the senior officer and held it until returned by the senior officers. Kudos.