US millionaire Dennis Tito celebrates after landing near the Kazakh town of Arkalyk following his trip as the world's first space tourist in 2001.

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Four astronauts are scheduled to return home from the International Space Station this week, capping off a nearly six-month mission in space, but rough weather at the crew’s splashdown site is forcing a delay.

Dennis Tito, a US millionaire who previously paid his way to the International Space Station in 2001, and his wife, Akiko, plan to take a lunar expedition that will last roughly a week, according to SpaceX.

The mission will come only after SpaceX fulfills its commitment to launch billionaire payments processing CEO Jared Isaacman on the first commercial human spaceflight mission on Starship, a rocket and spacecraft system that is still under development at SpaceX facilities in South Texas. Starship is awaiting approval from federal regulators to make its first uncrewed orbital test flight.

SpaceX will also carry out its first trip around the moon for billionaire fashion mogul Yusaku Maezawa, a mission announced years ago, before Tito’s trip, according to a news release.

Tito said during a news conference Wednesday afternoon that the only difference between his mission and Maezawa’s will be that he and his wife only purchased individual seats on the mission, while Maezawa purchased an entire flight for himself and a group of artists.

“The mission now is open for 10 others to sign up as well,” Tito said. He added he is not expecting this flight to launch in the near future, as he hopes SpaceX will launch “hundreds” of flights — including uncrewed satellite launches — before he and his wife fly.

“This was a long pursuit, dream of mine that began in 1958 when I started to study aeronautics and astronautics,” Tito said. “If I can show that a man over 80 years of age can accomplish this hopefully that will inspire people of any age … that this is possible.”

Akiko Tito, who said she is an engineer, pilot and investor, added that she hopes this mission will raise awareness about the new possibilities arising in spaceflight travel.

Dennis Tito earned a master’s degree in engineering science in 1964 and went on to work at NASA’s Jet Propulsion Laboratory in Pasadena, California, before leaving for a job in the financial industry in 1972, according to his biography on the encyclopedia website Britannica. He declined on Wednesday to share any financial information about the upcoming Starship mission.

Aarti Matthews, SpaceX’s director of Starship crew and cargo programs, said that SpaceX booking private missions on Starship is part of the company’s goal to offer “airline-like” access to space.

Tito, who is 82, became the first person ever to pay his way to space 21 years ago when he booked a ride with a company called Space Adventures. That company booked a handful of rides to space by purchasing seats aboard Russian Soyuz spacecraft in the early 2000s.

Now, commercial space companies, including SpaceX, are looking to follow up on those earliest days of space tourism by selling seats aboard newly developed, US-made spacecraft.

It’s not clear when the first crewed Starship mission will take off, however. That spacecraft is expected to be the follow-up to the capsule called Crew Dragon that SpaceX designed and built to carry NASA astronauts to and from ISS. The company has already launched private customers, including Isaacman, aboard that vehicle.

But Starship is far bigger than anything that SpaceX — or any other rocket developer — has ever built. It’s expected to have more thrust than both NASA’s Saturn V rocket, which powered the moon landings of the mid-20th century, and the space agency’s new moon rocket, called SLS, or Space Launch System. The company has long billed it as having the vehicle that could one day put humans on Mars for the first time, and NASA has reserved the vehicle to return astronauts to the lunar surface later this decade.

SpaceX CEO Elon Musk has, however, said he plans to carry out Starship test launches and missions with no crew — only satellites — before putting people on board.

Before that can happen, the Federal Aviation Administration, which licenses commercial rocket launches, must give the company approval.

When reached by email Wednesday morning, an FAA spokesperson said only that the agency will “make a license determination only after SpaceX provides all outstanding information and the agency can fully analyze it.”