Boeing capsule astronauts remain at Space Station with no return date, NASA says

Boeing Starliner's first astronaut-crewed capsule, which launched to the International Space Station (ISS) on June 5, remains docked at the station with no official return date, NASA said Thursday.

"We don't have a major announcement today relative to a return date," NASA Commercial Crew Program Manager Steve Stich said during a joint press conference with Boeing officials.

"We're making great progress, but we're just not quite ready to do that," Stich added.

What was initially planned to be an eight-day mission, has now spanned over 50 days, with veteran NASA astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams' return to Earth delayed until at least August, according to officials.

Thruster failures that caused issues on the launch trip to ISS and helium leaks on the Starliner capsule have led to continued delays, according to Boeing.

The Aerospace giant has been testing the capsule's propulsion system in White Sands, New Mexico, to identify the cause of the issues, according to Stich, who said analysis of the findings will be done this weekend.

In order to get the go-ahead for a return mission, NASA must review Boeing's engineering, which may not happen until the first week of August, Stich said.

On June 11, Boeing officials said the capsule was experiencing five "small" helium leaks as its first astronaut-crewed flight test continued.

Helium is used to pressurize the spacecraft's reaction control system (RCS) maneuvering thrusters, allowing them to fire, according to Boeing.

"Our focus today is to return Butch and Suni on Starliner," Stich said of the astronauts. "I think we're starting to close in on those final pieces of the flight rationale to make sure we can come home safely and that's our primary focus right now."

Mark Nappi, vice president and program manager of the commercial crew program at Boeing, was asked if there were any regrets about the mission.

"I think the only thing we'd do differently, is we would not have been so empathic about an eight-day mission," Nappi said of the repeated delays. "We kept saying 'eight-day minimum mission,' I think we all knew it was going to go longer than that, it's my regret that we didn't just say 'we're gonna stay up there until we get everything done we want to go do.'"

ABC News' Gina Sunseri contributed to this report.