All of the Mercury Seven eventually flew in space. They piloted all the spaceflights of the Mercury program that had an astronaut on board from May 1961 to May 1963, and members of the group flew on all of the NASA human spaceflight programs of the 20th century – Mercury, Gemini, Apollo, and the Space Shuttle. Shepard became the first American to enter space in 1961, and later walked on the Moon on Apollo 14 in 1971. Grissom flew Mercury and Gemini missions, but died in 1967 in the Apollo 1 fire; the others all survived past retirement from service. Schirra flew Apollo 7, the first Apollo mission, in Grissom’s place. Slayton, grounded with an atrial fibrillation, ultimately flew on the Apollo–Soyuz Test Project in 1975. Glenn became the first American in orbit in 1962, and flew on the Space Shuttle Discovery in 1998 to become, at age 77, the oldest person to fly in space. He was the last living member of the Mercury Seven when he died in 2016 at the age of 95.