NASA and Boeing announced Wednesday that the first crewed flight of the Starliner spacecraft will now take place no earlier than July 21. This moves the vehicle's flight, carrying NASA astronauts Suni Williams and Butch Wilmore, from the previously announced timeframe of April.

The manager of NASA's Commercial Crew program, Steve Stich, said the delay was attributable to the extra time needed to close out the pre-flight review process of Starliner and also due to traffic from other vehicles visiting the space station in June and the first half of July.

"When we look at all the different pieces, most of the work will be complete in April for the flight," Stich said during a teleconference with reporters. "But there's one area that's extending out into the May time frame, and this really has to do with the certification products for the parachute system."

Boeing has conducted more than 20 tests of its parachute system, including dropping the vehicle from different altitudes to test their deployment sequence and how the parachutes perform in different environments to simulate returning from space. Stich said there are no issues with the parachutes, which are installed on Starliner already. Mostly, it is about reviewing all the tests Boeing has done to ensure the parachutes performed as intended.

"It's just a matter of going through all that data and looking at the data and making sure we're really ready to go fly safely," Stich said.

There is one final test to be completed on the ground, he said, of a parachute subsystem that pulls Starliner's forward heat shield away and sets up deployment of the drogue and then main parachutes. That test is targeted for May.

The additional time needed to complete the review process of Starliner and its parachute system delayed the vehicle's launch into June. However, at that time, NASA plans to launch SpaceX's CRS-28 cargo resupply mission, which will tie up one of the lab's docking hatches. This supply mission is bringing solar arrays to the station that NASA does not want to delay because it would delay planned spacewalks to install them. The lack of a docking port, therefore, pushed the Starliner flight into the second half of July.

NASA and Boeing must also balance schedules with United Launch Alliance, which is boosting the mission to orbit with its Atlas V rocket. The company presently has the USSF-51 mission scheduled for the Space Force this summer and also needs the Space Launch Complex-41 pad for the debut of its Vulcan rocket in May or later this summer.

This will be the third flight of Boeing's Starliner spacecraft. The vehicle's debut in December 2019 failed to rendezvous with the International Space Station after multiple issues, including software problems. After fixing these issues, Boeing flew the vehicle on a second test flight in May 2022. Although there were some propulsion issues with this flight, Starliner docked with the space station, setting the stage for a crewed flight test.

After Boeing completes this critical test flight and NASA certifies the vehicle as ready for operational missions, the company will fly approximately once a year to the space station for regular crew rotations. The first of these operational missions is planned for no earlier than the spring of 2024.