Before becoming an astronaut, Armstrong was in the United States Navy and saw action in the Korean War. After the war, he served as a test pilot at the National Advisory Committee for Aeronautics (NACA) High-Speed Flight Station, now known as the Dryden Flight Research Center, where he flew over 900 flights in a variety of aircraft. As a research pilot, Armstrong served as project pilot on the F-100 Super Sabre A and C aircraft, F-101 Voodoo, and the Lockheed F-104A Starfighter. He also flew the Bell X-1B, Bell X-5, North American X-15, F-105 Thunderchief, F-106 Delta Dart, B-47 Stratojet, KC-135 Stratotanker and Paresev. He graduated from Purdue University and the University of Southern California.
His first spaceflight was aboard Gemini 8 in 1966, for which he was the command pilot, becoming one of the first U.S. civilians to fly in space (Joseph Albert Walker was the first US civilian in space several years earlier). On this mission, he performed the first manned docking of two spacecraft together with pilot David Scott. Armstrong's second and last spaceflight was as mission commander of the Apollo 11 moon landing mission on July 20, 1969. On this mission, Armstrong and Buzz Aldrin descended to the lunar surface and spent 2½ hours exploring while Michael Collins remained in orbit in the Command Module. Armstrong is a recipient of the Congressional Space Medal of Honor.