"This is a tragic day for the NASA family but also for the American people." -- NASA Administrator Sean O'Keefe
"To have this happen with 15 minutes to go until it was over was just unbelievable." -- Daniel Salton, whose sister, Laurel Clark, was aboard Columbia.
May 5, 1961: U.S. launches first American, astronaut Alan Shepard Jr., into space, on a 15-minute, 22-second suborbital flight.
May 25, 1961: President Kennedy declares the American national space objective to put a man on the moon.
Feb. 20, 1962: John Glenn becomes first American to orbit Earth.
July 20, 1969: Neil Armstrong and Edwin Aldrin of Apollo XI spend 21½ hours on the moon, 2½ of those outside the capsule.
Dec. 7-19, 1972: Apollo 17 mission that includes the longest and last stay of man on the moon - 74 hours, 59 minutes - by astronauts Eugene Cernan and Harrison Schmidt.
April 12, 1981: Shuttle Columbia becomes first winged spaceship to orbit Earth and return to airport landing.
June 18, 1983: Sally Ride becomes first American woman in space.
Jan. 28, 1986: Challenger shuttle explodes 73 seconds after launch, killing its crew of seven.
June 29, 1995: Atlantis docks with Mir in first shuttle-station hookup.
May 29, 1999: Discovery becomes first shuttle to dock with the international space station, a multinational, permanent, orbiting research laboratory.
Nov. 2, 2000: An American and Russian crew begins living aboard the international space station.
Feb. 1, 2003: Shuttle Columbia breaks apart over Texas, 16 minutes before it was supposed to land in Florida.