Originally scheduled to launch a crew of four to the International Space Station (ISS) in mid-August 2024, the mission was delayed by more than a month due to technical issues with the Boeing Starliner Calypso spacecraft that was docked at the ISS for the Boeing Crew Flight Test.

The mission was initially planned to transport four crew members—NASA astronauts Zena Cardman, Nick Hague, and Stephanie Wilson, along with Roscosmos cosmonaut Aleksandr Gorbunov—to the International Space Station (ISS).

Cardman was assigned to be the commander and Hague the pilot, while Wilson and Gorbunov would serve as mission specialists.

[4] Prior to the official announcement, Ars Technica reported that there was disagreement within NASA over who should fill the commander's seat in those six days.

[5] Following the crew changes, SpaceX, NASA, Cardman, Hague, Wilson, and Gorbunov collaborated for three weeks to identify how Hague could assume many of the tasks typically divided between the commander and pilot, and determine which tasks could be assigned to Gorbunov, who would sit in the pilot's seat during launch.

While Gorbunov is a qualified engineer and holds the rank of test cosmonaut (making him eligible to be a Soyuz commander), he had only previously received basic training on the Dragon in his role as a mission specialist.

The move allowed astronauts and critical cargo to return to Kennedy Space Center more quickly after splashdown, and SpaceX opened a facility in Florida to take in capsules after flight and prepare them for the next mission.

Following a successful static fire and final dress rehearsal on Tuesday, the SpaceX Dragon and Falcon 9 rocket were rolled back to the hangar on Wednesday, 25 September, as a precaution against potential weather impacts from Hurricane Helene, which was forecast to make landfall near the Florida panhandle on Thursday, 26 September.

[19] Crew-9 was able to lift off on the first attempt on 28 September at 17:17:21 UTC (1:17:21 pm EDT, local time at the launch site).

[22] After lifting the Dragon and second-stage to an altitude of 70 kilometers (43 mi; 38 nmi) the rocket's first stage, Booster 1085 returned to the Cape Canaveral Space Force Station and touched down at Landing Zone 1, seven minutes and 36 seconds after launch, completing its second flight.

[24] A few hours later, when the second stage was commanded to make a destructive reentry, it experienced an off-nominal deorbit burn, deviating from its planned trajectory.

SpaceX typically commands its second stages to re-enter the atmosphere and land in the ocean to minimize orbital debris.

The off-target landing increased the potential risk of harm, as aircraft and mariners were not instructed to avoid the area.