Human spaceflight is spaceflight with a crew or passengers aboard a spacecraft, often with the spacecraft being operated directly by the onboard human crew. Spacecraft can also be remotely operated from ground stations on Earth, or autonomously, without any direct human involvement. People trained for spaceflight are called astronauts, cosmonauts, or taikonauts; and non-professionals are referred to as spaceflight participants or spacefarers. The first human in space was Soviet cosmonaut Yuri Gagarin, who launched on 12 April 1961 as part of the Soviet Union's Vostok program. This was towards the beginning of the Space Race. On 5 May 1961, Alan Shepard became the first American in space, as part of Project Mercury. Humans traveled to the Moon nine times between 1968 and 1972 as part of the United States' Apollo program, and have had a continuous presence in space for 21 years and 279 days on the International Space Station.