Thanks to technical problems with their Boeing Starliner spacecraft, Sunita Williams and Barry Wilmore have spent a lot more time on the International Space Station than originally planned. After around nine months in space, they are returning to Earth aboard a SpaceX capsule with two other astronauts. The spacecraft has already begun its 17-hour journey and will splashdown on the evening of March 18.

But these astronauts were not the first spacefarers to get “stranded” in space, and they probably won’t be the last.

Dealing with such difficulties is an essential task for an astronaut—and Williams and Wilmore might have been secretly pleased with the situation.

“Astronauts consider themselves ‘stranded’ on Earth, so this is a huge gift,” says Chris Hadfield, a former NASA astronaut, space shuttle pilot and long-term crew commander on the ISS. “It’s the purpose of our profession.”

Call it a “stranding”, a delay, or an extended mission, astronauts spend extra time in space every now and then. Reasons vary from the geopolitical to natural hazards of space travel. But whatever the cause, astronauts and space agencies prepare for these scenarios.

Williams and Wilmore were scheduled to spend eight days on the ISS, after arriving there on the Starliner’s first flight in June of 2024.

But even before the launch and during the journey to the ISS, Starliner was plagued by leaks of the helium gas used to push fuel into its thrusters. NASA and Boeing tried to work through the problems, but in August, NASA announced their plan for Williams and Wilmore to return on the next SpaceX Dragon spacecraft scheduled to bring a crew back to Earth.

Starliner made its own automated descent, landing in New Mexico in September 2024. But Williams and Wilmore had to wait for a SpaceX relief team to reach the ISS. That crew finally arrived on Sunday, after dealing with their own battery and hydraulics issues.

That means the two astronauts spent roughly 286 days on the ISS—where missions typically only run as long as six months.

Hadfield, formerly a U.S. Air Force and U.S. Navy test pilot, says issues are expected during the first flight of any spacecraft; but he adds that he understands why NASA has acted to ensure the crew’s safety.

For astronauts, the more time in space, the better. “You train for decades so that you have an opportunity to spend extended periods of time in space—and this turned their short duration flight into a long-duration flight,” he notes.  

As experienced astronauts, Williams and Wilmore probably would have responded positively to the delay, speculates Hadfield, who now writes thrillers set on Earth and in space.

“At the end of each of my spaceflights, if someone had said ‘you get another three months up there’—that would have been the best thing,” he says.

NASA insists that Williams and Wilmore were technically not “stranded” in space, arguing that they expected the first Starliner flight to expose such problems.

But there’s a long history of spacefarers who have spent more time than expected in space because of barriers in bringing them back to Earth. (Here’s a brief overview of human spaceflight since 1961.)

The most famous case is that of Sergei Krikalev, a cosmonaut on board the Mir space station during the dissolution of the Soviet Union. Krikalev had launched on May 18, 1991, from Baikonur in the Soviet Socialist Republic of Kazakhstan and planned to spend about 150 days on Mir. But the Soviet Union fell apart during his mission, and issues about who would pay for his return kept him in orbit for 311 days—a world record at the time.

Sometimes spacecraft encounter problems while docked at the ISS, as was the case for another extended ISS occupant, American astronaut Frank Rubio. Rubio and two Russian cosmonauts arrived at the ISS on a Russian Soyuz spacecraft in September 2022, and they were scheduled to take the same spacecraft back in March 2023.

But the Soyuz developed problems after it was struck by a micrometeoroid—a speck of dust or rock traveling extremely fast—and so Rubio had to catch a ride on a different Soyuz in September later that year.

As a result, Rubio set a new record for the most time continuously spent in space by a NASA astronaut, of 371 days. However, that’s still shy of the overall record: Russian cosmonaut Valeri Polyakov spent 437 consecutive days on board the Mir space station in 1994 and 1995. (Read about how time in space changes astronauts.)

Two American astronauts and a Russian cosmonaut were stuck on board the ISS in February 2003, after the space shuttle Columbia disintegrated during its reentry to the atmosphere, killing all seven astronauts on board.

After the disaster, NASA suspended all space shuttle flights until they could be made safe — a grounding that lasted more than two years—and so the shuttle Atlantis scheduled to bring the crew back to Earth in March couldn’t fly. Eventually all three spent an extra three months on the ISS, returning in May 2003 on a Russian Soyuz spacecraft.

For a time, Russia’s Soyuz was the only spacecraft that could dock with the ISS, and problems with it sometimes caused delays in changing the space station’s crews. This includes the MS-10 mission, which was aborted shortly after its launch in October 2018.

Such delays, however, are seldom detailed by the Russian space agency Roscosmos; and Hadfield says changes in space flight schedules happen all the time.

The most dramatic case of a space stranding was during the Apollo 13 mission in 1970, after an oxygen tank on the command module exploded just three days into its six-day journey to the moon and back.

The disaster threatened the lives of the three astronauts on board. But they were able to use their lunar lander as a lifeboat, ditching it for the heat-shielded command module just before reentry; and they splashed-down safely on 17 April, 1970—roughly 14 hours later than originally expected.

University of Southern California astronautics professor Mike Gruntman says it is not usually an issue when astronauts have to spend more time in space than they expected.

But staying in space for extended periods might be more dangerous for older astronauts, who could suffer from the effects of muscle-loss and bone-loss in a microgravity environment, he says. (Here’s what we know about how spaceflight impacts the human body.)

If anything, the Starliner situation exemplifies the ability of career astronauts to deal with problems.

But it also shows how geopolitical issues can have an impact on spaceflight, he says, noting that the current conflict between Russia and Ukraine makes it “unrealistic” to consider an emergency Soyuz launch to bring the astronauts back.

Purdue University astronautical engineer Barrett Caldwell also sees the Starliner situation as a testament to the resilience of human spaceflight.

“The spaceflight community puts a tremendous additional burden of safety and management of risk on any vehicle which is designed for humans,” he says. “The recent decisions show how much we are living that reality.”

In addition, exposing and overcoming technical issues is part of the plan for new spacecraft: “Since this is a first mission of an experimental vehicle, all of this is part of the development and evaluation process,” says Caldwell.

As for how the Starliner crew spent their extra time in space, Williams and Willmore effectively joined the existing space station crew, living and working in space.

Former NASA astronaut Tom Jones speculated that NASA and its partners were probably "glad to have the extra productivity onboard, with two extra brains and pairs of hands with which to conduct research and maintain the very complex ISS.”

The ISS already stocks four months of emergency supplies for seven people, he noted. Several robot cargo ships also docked at the station during their time aboard, bringing extra supplies and personal items for the extra astronauts.

Any discomfort from an extended stay comes with the territory for career astronauts. “You don’t become an astronaut for comfort,” says Hadfield.

And Williams and Wilmore spent much of their lives training for just this sort of eventuality: “This is like the best Christmas present they both could have,” he says. “I would trade places with them in a heartbeat.”