2 months after Starliner launched, astronauts still haven’t returned: See timeline

• June's launch marked a critical milestone for Boeing as the first Starliner flight with astronauts aboard.
• But two months to the day since the launch, NASA astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams still remain at the International Space Station with no return date set.
• The delays in their trip back to Earth come after Boeing experienced a few launch scrubs before Starliner even made it to orbit.

Just as a slew of obstacles and mishaps delayed the launch of the Boeing Starliner time after time, so too has the return of the spacecraft's astronaut crew been postponed again and again.

It took a team of engineers about a month just to get Boeing's CST-100 Starliner prepared for its trip to the International Space Station after its initial launch date on May 6 was scrubbed at the last minute. When the capsule finally reached orbit June 5 while perched atop an Atlas V rocket built by United Launch Alliance, things were finally looking up for Boeing – in both a literal and figurative sense.

The company had for years sought to prove that its Starliner could compete with the likes of Elon Musk's SpaceX as one of two companies making routine trips to orbit on NASA’s behalf. After its first uncrewed test flight in 2019, June's launch marked a critical milestone as Starliner first flight with astronauts aboard.

NASA astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams were tentatively scheduled to spend little more than a week aboard the International Space Station once their capsule docked on June 6, a day after launching from the Kennedy Space Station in Cape Canaveral, Florida.

But two months after Starliner launched, the pair still remain in orbit at the space station with no return date set.

Here's a look at the major moments of the Boeing Starliner's inaugural crewed mission, including scrubs, launch and return delays.

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May 6: Starliner launch called off hours of liftoff

Years in the making, the third and final orbital flight test for Starliner was scheduled for launch until it is called off within hours of liftoff when engineers detected an anomaly on the pressure regulation valve in the liquid oxygen tank of the rocket's upper stage, according to NASA. The United Launch Alliance later says in a statement that the cancellation was "out of an abundance of caution for the safety of the flight and pad crew."

Days later, Wilmore and Williams return to Houston to spend extra time with their families as mission engineers work to fix the issues ailing Starliner.

NASA eyes May 17 as a potential mission launch after the United Launch Alliance initially said that the launch would not be able to take place any earlier than May 10. Mission engineers requested the extended delay in order to have time to replace the faulty value, NASA said.

On May 21, the team is able to replace the valve and re-pressurize the system, but then engineers encountered another obstacle: a small helium leak in Starliner's service module. The issue required the launch date to be pushed back once again, this time indefinitely.

June 1: Starliner prepares to launch again, scrubbed again

On June 1, The Starliner appears poised to finally take off. NASA decided to continue with the launch without repairing the helium leak, as the chemical used in spacecraft thruster systems is not combustible or toxic. However, the launch is once again scrubbed, this time minutes before liftoff due to a computer issue, NASA said on X, formerly Twitter.

The crew passes on a possible launch the next day and NASA instead eyes a launch window beginning June 5.

June 5: Starliner finally launches

On June 5, the Starliner, at long last, launches. Boeing Space shares a post on X at 11:44 a.m. confirming Starliner had reached a stable orbit and had broken away from the Atlas V rocket. From there, the craft began firing its own engines as it powered onward to the International Space Station, NASA said.

The following day, the Starliner docks at 1:34 p.m. EDT on the forward-facing port of the International Space Station's Harmony module. However, the night before, NASA shares an update unveiling that two more helium leaks had been discovered on the spacecraft occurring after Starliner arrived in orbit.

June 9: NASA announces astronauts will not return on date originally planned

Though Wilmore and Williams were only slated to spend a week on the space station, NASA announces on X that the Starliner and its two astronauts would likely land in the New Mexico desert no earlier than June 18. The space agency said the additional time at the space station was for the astronauts to assist with a spacewalk and to allow engineers more time to complete system checkouts of Starliner.

June 14: Astronauts return delayed again

The return is delayed a second time, with the astronauts now slated to undock from the International Space Station no earlier than June 25, landing June 26 at the White Sands Space Harbor in New Mexico, Boeing said in an update. While the spacecraft is cleared for crew emergency return scenarios, Boeing said the extra time allows the team to finalize departure planning and operations.

June 21: And again

Boeing and NASA once again delay the return home of Williams and Wilmore until July at the earliest. This time the agencies cite "a series of planned International Space Station spacewalks while allowing mission teams time to review propulsion system data." However, the agencies explain that the astronauts are by no means stranded in space, as supplies on the space station are plentiful and the pair can assist in station operations.

July 10: Astronauts aren't 'complaining' about being in space

Wilmore and Williams appear in a NASA telecast from the International Space Station. During seperate new conferences, Williams says, "I'm not complaining, Butch isn't complaining that we're here for a couple extra weeks." Meanwhile, scientists and engineers work through testing to better understand and resolve problems that occurred during Starliner's launch and flight, including some misfiring thrusters and helium leaks.

July 25: NASA, Boeing say there is still no return date

NASA and Boeing say in a press conference that the Starliner still does not yet have an official return date. However, NASA Commercial Crew Program Manager Steve Stich says, "We're making great progress."

Stich also shares that NASA has contingency options for returning Butch and Sunni to Earth, but right now the focus is on finishing up the tasks necessary to do so on Starliner.

August: Astronauts work at ISS while planning for return home

Wilmore and Williams, both Navy test pilots before they joined NASA, were to spend their limited time at the International Space Station testing the Starliner spacecraft and its subsystems.

With their stay indefinitely extended, the astronauts, both of whom had ventured to space twice before, have helped the space station crew with other operations while helping plan a return date when they can, NASA and Boeing have said.

Most recently, NASA and Boeing said engineers completed a hot fire test of the Starliner spacecraft’s reaction control system jets on July 27 to evaluate the spacecraft’s propulsion system. Wilmore and Williams were both seated inside the docked spacecraft during the test.

The astronauts then spent Tuesday practicing for undocking during a simulation, Boeing said in a Wednesday update.

Their return to Earth is expected to take place in August ahead of a station crew turnover. Meanwhile, while planning for that return continues into this week, NASA has indicated intentions to host a media briefing to share information about the agency’s "return readiness review preparations."

Once Williams and Wilmore are set to return to Earth, the astronauts will board the capsule, which will land in the American Southwest using parachutes that will slow it down to 4 mph before inflating large airbags.

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Starliner mission is crucial for Boeing

A successful mission would provide NASA with a second operational spacecraft to carry astronauts to the International Space Station as the U.S. space agency pivots to more partnerships with private industry.

As part of NASA’s commercial crew program, Boeing was awarded $4.8 billion, while its competitor, SpaceX, was awarded $3.1 billion in 2014 to develop their respective spacecraft, Florida Today reported.

But while Boeing's project has lagged behind schedule for years, racking up $1.5 billion in unplanned development costs along the way – as reported by Reuters – SpaceX has already begun reliably transporting astronauts and supplies to the space station.

Boeing's Starliner had conducted two uncrewed missions before Williams and Wilmore went into orbit aboard the Starliner – each plagued by woes and technical issues.

Dozens of software and engineering issues resulted in the failure of the first attempt in 2019 to send an uncrewed Starliner to the ISS for a week. While it reached orbit, the capsule failed to reach the space station and instead returned to Earth, according to Florida Today.

The follow-up flight test in 2022 met standards of docking to the space station and successfully landed, but not without the discovery of multiple concerns as Boeing crews inspected the spacecraft later, Florida Today reported.

Needless to say, Boeing's ability to join SpaceX and earn certification from NASA for crewed rotation missions to the space station hinges on what comes next with its Starliner.

Contributing: Mary Walrath-Holdridge, Gabe Hauari, Emily DeLetter, James Powel, Mike Snider, Natalie Neysa Alund and Jonathan Limehouse, USA TODAY

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com