NASA astronauts stranded in space until next year said they did not feel let down by Boeing but admitted to "tough times", the German Press Agency (dpa) reported.
Boeing's first astronaut mission ended earlier this month with its Starliner capsule returning to Earth, while test pilots Barry "Butch" Wilmore and Sunita Williams remained in space.
Wilmore said, "We found some things that we just could not get comfortable with, putting us back in the Starliner when we had other options."
NASA has announced that the pair will instead return on a SpaceX craft in February, stretching their original eight-day mission to more than eight months.
Speaking at a press conference on Friday from the International Space Station, Wilmore said, "It's been quite an evolution over the last three months. We've been involved from the beginning through all the processes of assessing our spacecraft, Calypso.
"And it was trying at times. There were some tough times all the way through.
"You certainly, as the commander and the pilot of your spacecraft, don't want to see it go off without you, but that's where we wound up."
Asked if he felt let down by Boeing after Starliner returned to Earth without its crew, Wilmore responded, "Let down? Absolutely not.
"Never entered my mind. I don't think Suni's either until you mentioned it."
Wilmore added that Boeing was "on board" with "changes that need to be made" after the company's Starliner capsule returned to Earth without its crew.
The astronaut told the press conference, "Obviously, when you have issues like we've had, there are some changes that need to be made.
"Boeing's on board with that. We're all on board with that."
He continued, "When you push the edge of the envelope again and do things with spacecraft that have never been done before, just like Starliner, you're going to find some things.
"And in this case, we found some things that we just could not get comfortable with, putting us back in the Starliner when we had other options.
"There have been many cases in the past where there were no other options.
"We were very fortunate that we have the Space Station, and we had the option to stay and the option to come back a different way."