Leroy Gordon Cooper Jr. was a U.S. Air Force test pilot and one of NASA's original Mercury Seven astronauts, the youngest of the group. He flew the last Mercury mission, Faith 7, in 1963 and the record-setting Gemini 5 in 1965. He later became one of the best-known astronauts to speak openly about UFOs, describing sightings over West Germany and a 1957 film taken at Edwards Air Force Base.

Cooper was born on March 6, 1927, in Shawnee, Oklahoma. After Marine Corps service and study at the University of Hawaii, he joined the Air Force and flew fighters with the 86th Fighter Bomber Group in West Germany. After earning a degree in aeronautical engineering from the Air Force Institute of Technology in 1956, he attended the Experimental Flight Test School at Edwards Air Force Base. He stayed on as a project engineer and test pilot on the F-102A and F-106B. NASA announced him as one of its first seven astronauts on April 9, 1959.

On May 15, 1963, Cooper launched aboard Faith 7. He orbited Earth 22 times in 34 hours, 19 minutes and 49 seconds and became the first American to sleep in orbit. When power and electronics failures crippled the capsule, he judged his reentry attitude by hand, using his wristwatch and lines he had marked on the window, and fired the retrorockets himself. In August 1965 he and Pete Conrad flew Gemini 5, an endurance record of nearly eight days, which made Cooper the first person to make a second orbital flight. He retired from NASA and the Air Force as a colonel on July 31, 1970, later held business posts including research and development at Disney, and passed away on October 4, 2004, in Ventura, California.

Cooper said he first saw UFOs while flying over West Germany in 1951. His best-known claim concerns May 3, 1957, when, by his account, cameramen James Bittick and Jack Gettys filmed a saucer-like craft that landed silently on a dry lake bed at Edwards and then took off. Cooper said he had the film developed, looked at the negatives, and sent everything to the Pentagon without keeping prints. He said he never learned its fate and assumed it went to Project Blue Book. He denied reports that he had seen a UFO during Faith 7. In a 1978 letter to Grenada's mission at the United Nations, then pressing for a UN study of UFOs, he wrote that he believed "extraterrestrial vehicles and their crews are visiting this planet." His 2000 memoir with Bruce Henderson, Leap of Faith, retold these stories. The space historian Robert Pearlman wrote that he struggled to see how Cooper accepted alien visits on little more than anecdote.

The government's 2026 UFO file releases revisited his NASA record. PURSUE Release 02 in May included Faith 7 audio in which Cooper reports "John's fireflies," which NASA attributes to frozen condensation drifting off the spacecraft. Release 03 in June added a 1962 Walter Cronkite interview, in which Cooper said "a large number of exceptionally well-qualified people have seen objects" without a "logical explanation," along with Gemini 5 debriefings. His standing as a Mercury astronaut has kept his UFO statements widely quoted, although the 1957 Edwards film he described has never been made public.