NASA picks SpaceX to bring home the American astronauts stuck in space. It's the latest blow to Boeing.

• Astronauts Butch Wilmore and Suni Williams will return to Earth on SpaceX's Crew Dragon.
• The astronauts have been stuck on the ISS since June due to issues with Boeing's Starliner.
• It's another blow to Boeing, which is competing with SpaceX to deliver NASA astronauts to space.

NASA has decided the lives of two astronauts stuck at the International Space Station will be in SpaceX's hands after weeks of intense deliberation and serious safety concerns.

NASA Administrator Bill Nelson made the announcement during a press conference on Saturday at the Johnson Space Center in Houston.

The two astronauts, Suni Williams and Butch Wilmore, have been on the ISS for 11 weeks. Their mission was originally supposed to last eight days.

The ordeal began when five of Starliner's 28 reaction control system thrusters failed as it traveled to the ISS in June. The spacecraft's helium system was also leaking.

Mission controllers have been working to resolve the issues and test the spacecraft ever since in the hopes they — and not someone else — could safely bring the astronauts home.

NASA leadership held an internal meeting earlier today to review whether Williams and Wilmore could safely return to Earth on Boeing's Starliner spacecraft or if they should rely on SpaceX's Crew Dragon instead.

"I want you to know that Boeing has worked very hard with NASA to get the necessary data to make this decision," Nelson said. "We want to further understand the root causes and understand the design improvements so that the Boeing Starliner will serve as an important part of our assured crew access to the ISS."

Nelson said he spoke with Boeing CEO Kelly Ortberg, who said the company would continue addressing issues with Starliner.

During a July press conference, a NASA official acknowledged that relying on SpaceX to retrieve the astronauts was an option but declined to provide details.

NASA confirmed its SpaceX backup plan this month and postponed the company's next launch to September 24. The delay allows Wilmore and Williams to fly home with the SpaceX crew on its four-person spacecraft in February, about eight months later than their initial schedule.

The SpaceX plan isn't without risks.

Wilmore and Wiliams arrived at the ISS in spacesuits compatible with Boeing's Starliner — not the Crew Dragon spaceship. Williams and Wilmore will have to travel to Earth without suits on the Crew Dragon spaceship, which does not guarantee as much protection for them, according to Fortune.

This is possibly the biggest safety decision NASA has had to make in decades. The Space Shuttle Columbia disaster, during which seven astronauts died, has weighed heavily on the minds of the Starliner mission managers, many of whom were involved in that failed flight, Ars Technica reported.

"I've been very hyper-focused lately on this concept of combating organizational silence. If you look at both, unfortunately, Challenger and Columbia, you can see cases where people had the right data or a valid position to put forward, but the environment just didn't allow it," Russ DeLoach, the chief of NASA's Office of Safety and Mission Assurance said in a briefing about the Starliner mission on August 14.

During the press conference, Nelson acknowledged that NASA has made mistakes in the past.

"Space flight is risky," he said. "Even at its safest. Even at its most routine. A test flight, by nature, is neither safe nor routine. So, the decision to keep Butch and Suni aboard the International Space Station, and bring the Boeing Starliner home un-crewed, is a result of a commitment to safety."

NASA funneled $4.2 billion into Starliner's development. The contract is part of the agency's Commercial Crew Program, an effort to give NASA multiple US-based options for human spaceflight rather than depending on Russian Soyuz spacecraft.

The Starliner's original mission was to prove that it could safely ferry astronauts to and from the ISS regularly. The failure of that mission is a serious blow to Boeing's space business, but NASA's comments on Saturday seem to indicate that it plans to continue working with the company.

Both Boeing and SpaceX have spent a decade working with NASA on their Starliner and Crew Dragon vehicles, respectively.

NASA always insisted the program was not a competition or a race, but if it had been, SpaceX would've won by a landslide. Not only did the company complete its first crewed test flight four years ago, as CEO Elon Musk pointed out ahead of Williams' and Wilmore's launch — it did it for cheaper, only costing NASA $2.6 billion.

After years of delays, technical issues, and rising costs, this Crew Flight Test was the last hurdle Boeing had to clear for NASA to certify Starliner for human spaceflight.