Washington, Apr 7 (IANS): NASA has updated its commercial crew contract with Boeing to let the US-based aerospace company fly three people to the International Space Station (ISS) who will stay there for up to six months from an earlier planned two-week trip.

The move is seen as to quickly end the dependency over Russian Soyuz flights to ferry astronauts to the ISS as NASA's contract with Soyuz ends in 2019.

"NASA has updated its Commercial Crew Transportation Capability (CCtCap) contract with Boeing, which provides flexibility in its commercial flight tests," the US space agency said on Friday.

Boeing, one of the agency's two commercial crew partners (the other being SpaceX), approached NASA last year and proposed adding a third crew member on its Crew Flight Test (CFT) to the ISS.

"The change includes the ability to extend Boeing's CFT from roughly two weeks to up to six months as well as the training and mission support for a third crew member. Cargo capabilities for the uncrewed and crewed flight tests were also identified," NASA said.

Adding a third crew member on Boeing's flight test -- scheduled for later this year -- could offer NASA an additional opportunity to ensure continued US access to the orbital laboratory.

"This contract modification provides NASA with additional schedule margin if needed," said William Gerstenmaier, Associate Administrator, Human Exploration and Operations Mission Directorate at NASA.

"We appreciate Boeinga¿s willingness to evolve its flight to ensure we have continued access to space for our astronauts. Commercial space transportation to low-Earth orbit from US soil is critical for the agency and the nation," he added.

The current commercial crew flight schedules provide about six months of margin to begin regular, post-certification crew rotation missions to the ISS.

"Turning a test flight into more of an operational mission needs careful review by the technical community," said Gerstenmaier.

For example, the spacecraft capability to support the additional time still needs to be reviewed.

"Modifying the contract now allows NASA and Boeing an opportunity to tailor the duration to balance the mission needs with vehicle and crew capabilities," NASA noted.

This would not be the first time NASA has expanded the scope of test flights.

NASA had SpaceX carry cargo on its commercial cargo demonstration flight to the space station under the Commercial Orbital Transportation Services (COTS) initiative in 2012, which was not part of the original agreement.

Boeing and SpaceX plan to fly test missions without crew to the space station this year prior to test flights with a crew onboard.

After each company's test flights, NASA will evaluate the in-flight performance in order to certify the systems and begin regular post-certification crew rotation missions.