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 Challenger disaster
After the accident, NASA's Space Shuttle fleet was grounded for almost three years while the investigation, hearings, engineering redesign of the SRBs, and other behind-the-scenes technical and management reviews, changes, and preparations were taking place. At 11:37 on September 29, 1988, Space Shuttle "Discovery" lifted off with a crew of five from Kennedy Space Center pad 39-B. It carried a Tracking and Data Relay Satellite, TDRS-C (named TDRS-3 after deployment), which replaced TDRS-B, the satellite that was launched and lost on "Challenger". The "Return to Flight" launch of "Discovery" also represented a test of the redesigned boosters, a shift to a more conservative stance on safety (e.g., it was the first time the crew had launched in pressure suits since STS-4, the last of the four initial Shuttle test flights), and a chance to restore national pride in the American space program, especially manned space flight. The mission, STS-26, was a success (with only two minor system failures, one of a cabin cooling system and one of a Ku-band antenna), and a regular schedule of STS flights followed, continuing without extended interruption until the 2003 "Columbia" disaster.