STS-5
"Columbia" landed on Runway 22 at Edwards Air Force Base on 16 November 1982, at 6:33 am PST, having traveled 2 million miles in 81 orbits during a mission that lasted 5 days, 2 hours, 14 minutes and 26 seconds. "Columbia" was returned to KSC on 22 November 1982. STS-5 was the first shuttle flight in which the crew did not wear pressure suits for the launch, reentry, and landing portions of the flight, similar to the Soviet Voskhod and Soyuz missions prior to the ill-fated Soyuz 11 mission in 1971.
The shuttle was formally declared "operational" after STS-4. However, the Columbia Accident Investigation Board (CAIB), in its report on the loss with all crew aboard of "Columbia" during STS-107 in 2003, asserted that the orbiter should never have been considered operational and that, while not intrinsically unsafe, it was in fact an experimental vehicle. The CAIB's rationale was that civilian and military aircraft that are considered operational must have been tested and proven over thousands of safe flights in their final operational configurations, whereas the shuttle had conducted under 200 flights, with continuous modification. NASA operated the Space Shuttle as an experimental vehicle for the remainder of the program.
Space Shuttle Columbia disaster
The second "Return to Flight" mission, STS-121, launched on July 4, 2006, at 2:37:55 pm (EDT), after two previous launch attempts were scrubbed because of lingering thunderstorms and high winds around the launch pad. The launch took place despite objections from its chief engineer and safety head. This mission increased the ISS crew to three. A crack in the foam insulation of the external tank gave cause for concern, but the Mission Management Team gave the go for launch. Space Shuttle "Discovery" touched down successfully on July 17, 2006 at 9:14:43 am (EDT) on Runway 15 at the Kennedy Space Center.