Space tourism company Virgin Galactic announced Monday that it is resuming flights with a mission this month, its first in nearly two years, and the launch of commercial trips in June.

The Unity 25 mission will take place in late May with four company employees on board, said Virgin Galactic, which was founded by British billionaire Richard Branson, who took part in the firm's last spaceflight in July 2021.

"Unity 25 is the final assessment of the full spaceflight system and astronaut experience before commercial service opens in late June," Virgin Galactic said in a statement.

Unity 25 will be the company's fifth trip into space, defined as 50 miles (80 kilometers) above sea level.

Unlike other companies that use vertical-launch rockets, Virgin Galactic uses a carrier aircraft that takes off from a runway, gains high altitude, and drops a rocket-powered plane that soars into space before gliding back to Earth.

The total journey time is 90 minutes, with passengers experiencing a few minutes of weightlessness in the space plane's cabin.

Virgin's flights launch from Spaceport America in New Mexico. 

The crew for the Unity 25 mission will be made up of two men and two women: Beth Moses, who has taken part in two previous Virgin Galactic flights, Jamila Gilbert, Chris Huie and Luke Mays, who spent several years training NASA astronauts.

Two pilots are also assigned to the mothership and two to the spaceship.

The first commercial flight, Galactic 01, will include passengers from the Italian Air Force.

The Virgin Galactic space program has suffered years of delays and a 2014 accident in which a pilot died.

Virgin Galactic has sold 800 tickets for future commercial flights -- 600 between 2005 and 2014 for $200,000 to $250,000 and 200 since then for $450,000 each.

Virgin Galactic is in competition in the space tourism business with Amazon founder Jeff Bezos' Blue Origin, which also offers short suborbital flights and has sent 32 people into space.

Blue Origin's New Shepard rockets have been grounded, however, since a September 2022 accident that occurred shortly after liftoff from Texas on an uncrewed flight.

Blue Origin said in March that it hoped to resume flights soon.

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