Washington, June 3 (IANS): NASA aims to buy from SpaceX five additional crewed flights to the International Space Station.

SpaceX is currently NASA's only certified commercial crew transportation provider.

In a statement, NASA said that it may need the additional flights "as early as 2026 to ensure dissimilar redundancy, maintain safe space station operations".

NASA announced a "sole source modification" as part of its existing Commercial Crew Transportation Capabilities (CCtCap) contract with SpaceX.

While the agency has not disclosed the expected value of the modified contract, it adds on to a $3.5 billion contract awarded to SpaceX in February for three additional astronaut missions with its Falcon 9 rocket and Dragon capsule: Crew-7, Crew-8 and Crew-9. NASA had at the time said that it may order more flights from SpaceX.

"Our goal has always been to have multiple providers for crewed transportation to the space station. SpaceX has been reliably flying two NASA crewed missions per year, and now we must backfill those flights to help safely meet the agency's long-term needs," said Phil McAllister, director, commercial space at NASA, in a statement.

SpaceX will fly its sixth rotational mission for NASA in the spring of 2023.

NASA, however, needs "additional missions from SpaceX to implement our strategy of having each commercial provider flying alternating missions once per year," McAllister added.

In 2014, NASA had awarded the CCtCap contracts to Boeing and SpaceX through a public-private partnership as part of the agency's Commercial Crew Programme.

Boeing's recent Orbital Flight Test-2, which went well, gives hope to certify the Starliner system for future missions, NASA said.

"The recent success of Boeing's uncrewed flight test is helping to solidify NASA's long-term goals," said Steve Stich, manager, NASA's Commercial Crew Programme.

"It's critical we complete Starliner's development without undue schedule pressure while working to position both Boeing and SpaceX for sustainable operations in the years ahead," he noted.