For the second time in seven months, NASA awards a mission to Boeing to transport crew to the International Space Station.

NASA today awarded a mission to Boeing to transport crew to the International Space Station (ISS) with flights beginning in 2017, marking the second time this year that Boeing has been awarded a crew rotation mission. In May, the agency awarded Boeing its first commercial human spaceflight mission.

Boeing will transport the crews using its Commercial Space Transportation-100 (CST-100) “Starliner” spacecraft.

The award is technically a task order to Boeing’s $4.2 billion Commercial Crew Transportation Capability contract. Boeing could provide as few as two and as many as six missions to the space station after completing human rating certification.

“As our company begins its second century, our Starliner program continues Boeing’s tradition of space industry innovation with commercial service to the space station,” said John Mulholland, vice president and program manager, Boeing’s commercial crew program. “We value NASA’s confidence in the Starliner system to keep their crews safe.”

Boeing met a series of development milestones in order to receive NASA’s “Authority to Proceed.” Several of these milestones were accomplished in 2015 including those demonstrating integrated design maturity, qualification test vehicle readiness and reviews demonstrating flight software and checkout and control systems maturity. Launch vehicle provider United Launch Alliance recently completed construction on the main column of the Starliner crew access tower at Space Launch Complex-41, the first crew tower to be built at Cape Canaveral, Fla., since the 1960s.