Boeing was among three companies who bid for the next NASA contract to take astronauts into space. The company offered its CST-100 space capsule in the competition. (Illustration by Boeing)

NASA’s independent safety panel accused the agency of a “lack of transparency” about its program to hire commercial space companies to fly astronauts to the International Space Station, saying the opacity could create increased safety risks.

In its annual report to Congress, the Aerospace Safety Advisory Panel said the lack of communication about critical safety measures “has been a concern for a number of years.” And it made it impossible for the panel “to offer any informed opinion regarding the adequacy of the certification process or the sufficiency of safety” in what is known as the “commercial crew” program.

The "failure to engage in open and transparent communication is reminiscent of the problems" surrounding the causes of the fatal Challenger and Columbia space shuttle disasters, according to the report released Wednesday.

Last year, NASA awarded contracts to Boeing and SpaceX to ferry astronauts to space in what was considered a major shift for the agency. Instead of owning and operating the spacecraft, NASA is essentially hiring the two companies to transport astronauts in an arrangement some have likened to a rental car agreement.

For Boeing, the contract is worth up to $4.2 billion; SpaceX, which said it could perform the work for less, was awarded a contract valued at $2.6 billion.

Although NASA has said it will ensure that the companies meet rigorous safety standards to be certified for the missions, the panel said the agency “is operating at relative arm’s length while concurrently fostering the development of a commercial market. The panel strongly believes open communication and transparency are essential to ensuring the safety of the program.”

In a statement, NASA Administrator Charles Bolden said that “safety remains our top priority.” Agency officials said they were unable to talk openly about the program while a third competitor for the contract, Sierra Nevada, protested the award. However, once the Government Accountability Office denied that protest earlier this month, NASA officials said they were able to more openly discuss their plans. In a news conference this week, they said that Boeing and SpaceX were making significant progress toward launching the first mission in late 2017 or early 2018.

The safety panel noted that after three years of asking for safety and certification information, it started to receive some late last year. But it said NASA was forthcoming only "after the panel made it clear that this failure to share information would be covered in this report."