Launch from Cape Canaveral (KSC); landing on Edwards AFB.

The launch occurred after a 1-month delay because of technical reasons. Ulf Merbold was the first non-American in a Space Shuttle. STS-9 carried the first crew of six persons and became the first mission of the ESA sponsored Spacelab (Spacelab 1, SL-1).

All in all 73 experiments were carried out in the fields of atmospheric and plasma physics, astronomy, solar physics, material sciences, technology, life sciences and Earth observations. The effort went so well that the mission was extended an additional day to 10 days, making it the longest duration Shuttle flight to that date.

Short time before reentry two guidance computer crashed, but one of them was succesfully rebooted. Just before landing two of the three auxiliary power units (APU's) caught fire due to a hydrazine leak, but the landing was succesful. The leak was later discovered after it burned itself out and caused major damage to the compartment.