WASHINGTON (NEXSTAR) – Two astronauts remain at the International Space Station, their return delayed because of problems with thrusters on the Boeing Starliner spacecraft. Another mission, set to depart next month, is in limbo, after a problem with the SpaceX Falcon 9 rocket.

NASA Administrator Bill Nelson said, despite the delays, NASA’s commercial crew mission has been a success.

“That has proven to be phenomenally successful,” Nelson said. “It’s a fixed price contract. It saves us a lot of money.”

Astronauts Barry “Butch” Wilmore and Suni Williams were scheduled to return to earth on June 14. While they approached the International Space Station, the Starliner had challenges with the thrusters. Nelson said NASA and Boeing want to continue testing the thrusters in space.

“To see how the valves operate in the vacuum of space,” Nelson said. “That’s a good example.”

Wilmore and Williams are the first people to fly on the Boeing Starliner.

“It’s a test flight. And you expect to test everything. And if something goes wrong, you fix it,” Nelson said.

Last week, SpaceX’s Falcon 9 rocket’s second stage failed to burn for the second time, the company posted on X. The un-crewed mission tried to deliver starlink satellites to orbit. The FAA has asked SpaceX to investigate, the agency said in an emailed statement. SpaceX has asked the FAA to allow Falcon 9 to continue flying during the investigation. The FAA said it is reviewing the request, in an email.

“When we launch our astronauts on the Falcon 9 and the second stage ignites, we do not have to ignite it the second time,” Nelson said. “The good news is that they know what the problem was and they’re going to fix it.”

Nelson said the public-private partnerships are vital to NASA’s future missions to the moon and beyond.