Space shuttles have played a pivotal role in the US space programme. They made their debut in 1981 and enabled Nasa to learn how to live and work in orbit. But the workhorse spacecraft proved more expensive and risky to fly than originally hoped.
Jan. 5, 1972 - President Richard Nixon signs a bill authorizing $5.5 billion to develop a reusable winged space transportation system called the space shuttle. The spacecraft were to be designed to carry seven astronauts and up to 50,000 pounds (22,680 kg) of cargo into orbits a few hundred miles from Earth.
Sept. 17, 1976 - The prototype shuttle Enterprise is unveiled, named after the spaceship in the popular TV show Star Trek. Without engines and a heat shield, Enterprise was never intended to fly in space. Instead, it was used for atmospheric flight, vibration and launch configuration tests.
April 12, 1981 - Space shuttle Columbia lifts off from the Kennedy Space Center in Florida on the programme's inaugural flight. Apollo veteran John Young and rookie Bob Crippen are aboard for the 54.5-hour trial run. It was the first U.S. manned spaceflight since the 1975 Apollo-Soyuz docking.
Nov. 11, 1982 - After four test flights, Nasa deems the shuttle an operational vehicle and doubles the crew size to four, including the first non-pilot astronaut, physicist Joe Allen. On its fifth flight, Columbia carries two satellites into orbit.
April 7, 1983 - Astronauts Story Musgrave and Donald Peterson conduct the shuttle programme's first spacewalk. Since then, shuttle astronauts have ventured out into open space another 161 times.
June 18, 1983 - Challenger takes off on Nasa's seventh shuttle mission with a five-person crew that includes Sally Ride, the first American woman in space. The next flight in August includes the first African-American astronaut, Guion Bluford.
Jan. 25, 1984 - President Ronald Reagan's State of the Union address directs Nasa to start working on a space station. The project, named Freedom, would fulfill the original post-Apollo US goal to have a space transportation system and a space station in orbit.
April 11, 1984 - Spacewalking astronauts repair the Solar Maximum Mission satellite, the first in-orbit satellite servicing.
April 12, 1985 - Convinced the shuttle is safe enough for non-professional astronauts to fly, Nasa launches shuttle Discovery on the programme's 16th flight with Republican Senator Jake Garn in the crew. A Saudi prince flies in June and then-US Representative Bill Nelson, a Florida Democrat who later became a senator, flew in January 1986.
Jan. 28, 1986 - Six astronauts and schoolteacher Christa McAuliffe are killed after a seal ruptures on one of the booster rockets carrying shuttle Challenger off the launch pad. Investigators cited poor management as a contributing cause of the accident.
Sept. 29, 1988 - A sobered and more safety-conscious Nasa returns the shuttle fleet to flight. Commercial satellites are booted off the manifest. The military, concerned about climbing programme costs and flight delays even before the accident, ramps up expendable launch vehicle production lines.
May 4, 1989 - The backlog of satellites awaiting launch after the Challenger accident includes science probes headed beyond Earth. Magellan, a Venus radar mapper, is the first shuttle-launched planetary spacecraft.
April 24, 1990 - After years of delay, the Hubble Space Telescope is carried into orbit aboard shuttle Discovery. Two months later, Nasa finds out it has a flawed primary mirror. The telescope is repaired by spacewalking astronauts in December 1993, the first of five service calls.
May 7, 1992 - Endeavour, the replacement shuttle for Challenger, lifts off to retrieve and relaunch a stranded communications satellite. The tools fail to work and the astronauts try an unprecedented three-man spacewalk to grab the spacecraft with their gloved hands and are ultimately successful.
Sept. 12, 1992 - The first married couple, Jan Davis and Mark Lee, fly together in space, along with the first Japanese astronaut and the first African-American woman. Nasa has a rule about couples flying together, but Davis and Lee married after they were assigned to the crew.
Dec. 2, 1992 - Discovery launches on the 10th and final mission for the U.S. military, a premature and ironic parting since the shuttle's design was dictated by Air Force cargo requirements.
Feb. 3, 1994 - The fall of the Soviet Union reverberates in the space programme. The United States and Russia begin an astronaut-cosmonaut exchange programme with Sergei Krikalev flying on the shuttle.
March 14, 1995 - Nasa astronaut Norm Thagard becomes the first American to fly on a Russian Soyuz rocket. Thagard joins the Russian Mir space station crew for a four-month mission.
June 29, 1995 - For the first time, the space shuttle docks at a space station, although not the one originally expected. Atlantis parks at Mir for the first US-Russian joint space mission, a harbinger of the International Space Station partnership to come.
July 13, 1995 - Shuttle Discovery launches on the 70th shuttle flight after a lengthy delay for fuel tank repairs. Nesting woodpeckers had drilled about 200 holes into the fuel tank's foam insulation over the Memorial Day weekend.
Oct. 29, 1998 - Mercury astronaut John Glenn, the first American in orbit, successfully lobbies for a second spaceflight. The former senator was 77, the oldest person to fly in space.
Dec. 4, 1998 - The shuttle finally begins work on its original mission of building a space station. Endeavour launches with the Unity connecting node, which is attached to the Russian base module already in orbit.
Oct. 31, 2000 - Nasa astronaut Bill Shepherd and cosmonauts Sergei Krikalev and Yuri Gidzenko launch aboard a Soyuz capsule to the fledging space station, becoming the first resident crew.
Feb. 1, 2003 - Shuttle Columbia breaks apart as it glides through the atmosphere for landing, killing all seven astronauts aboard. The shuttle was returning from a 16-day research mission. The crew included Israel's first astronaut, Ilan Ramon. The shuttle's heat shield failed due to damage from a debris impact during launch.
Jan. 14, 2004 - President George W. Bush releases his vision for space exploration, which redirects the human space programme to the moon and destinations beyond Earth. It calls for the shuttle's retirement upon completion of the space station.
Aug. 8, 2007 - Barbara Morgan, who originally trained as backup teacher-in-space to Challenger's Christa McAuliffe, launches with the shuttle Endeavour crew on a space station assembly mission. Morgan was admitted into the astronaut corps in 1998 and left the agency a year later.
Feb. 24, 2011 - Shuttle Discovery launches on its 39th and final flight with the last U.S. module for the space station. The shuttle is promised to the Smithsonian National Air & Space Museum.
May 16, 2011 - Shuttle Endeavour launches on its 25th and final flight with the $2 billion Alpha Magnetic Spectrometer particle detector. The shuttle is promised to the California Science Center in Los Angeles.
July 8, 2011 - Shuttle Atlantis launches on the 135th and final flight in the 30-year-old programme, a 13-day cargo run to the space station. The shuttle will be staying at the Kennedy Space Center in Florida, becoming a permanent exhibit at the Visitors Center.
July 21, 2011- Atlantis lands at Kennedy Space Center, Florida, for the final time at 5.57am local time. "Mission complete, Houston," Commander Chris Ferguson tells mission control.