Mark Kelly flew his first mission in 2001 as pilot of STS-108, piloted STS-121 in 2006, and commanded STS-124 in 2008 and STS-134 in 2011, the final mission of Space Shuttle Endeavour.
Head entity: STS-108
Tail entity: Mark Kelly
Relation (head \u2192 tail): astronaut mission
Inverse relation (tail \u2192 head): crew member