Washington, Mar 1 (IANS): NASA on Tuesday awarded three additional missions to the International Space Station (ISS) to Elon Musk led SpaceX company for a $3.49 billion contract.

The contract for Crew-7, Crew-8, and Crew-9 is part of NASA's Commercial Crew Transportation Capability (CCtCap), which follows the US space agency's notice of intent to procure the flights in December 2021, NASA said.

It brings the total missions for SpaceX to nine and allows NASA to maintain an uninterrupted US capability for human access to the space station.

As part of the missions, SpaceX's Crew Dragon spacecraft and Falcon 9 rocket transport up to four astronauts along with critical cargo to the space station.

Earlier, SpaceX was contracted to fly three more missions to the ISS: Crew-4 and Crew-5 in 2022 and Crew-6 in 2023.

With the extension, which is "fixed-price, indefinite-delivery/indefinite-quantity," NASA said in a statement.

The period of performance for SpaceX now runs through March 31, 2028, it added.

"It's critical we begin to secure additional flights to the space station now so we are ready as these missions are needed to maintain a US presence on station,a Kathy Lueders, associate administrator of NASA's Space Operations Mission Directorate, said in the agency's notice of intent to modify SpaceX's contract, published in December 2021.

"Our US human launch capability is essential to our continued safe operations in orbit and to building our low-Earth orbit economy," Lueders 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.

Under CCtCap, NASA certifies that a provider's space transportation system meets the agency's requirements prior to flying missions with astronauts.

Only SpaceX was certified by NASA for crew transportation in November 2020, and the company is currently on its third crew rotation mission for the agency.