The Shuttle fleet lost two orbiters and 14 astronauts in two disasters: "Challenger" in 1986, and "Columbia" in 2003. While the 1986 loss was mitigated by building the from replacement parts, NASA did not build another orbiter to replace the second loss. NASA's Space Shuttle program had 135 missions when the program ended with the successful landing of the Space Shuttle "Atlantis" at the Kennedy Space Center on July 21, 2011. The program spanned 30 years with over 300 astronauts sent into space.