SpaceX and Boeing, the two companies NASA ended up hiring to develop space transportation, may send a human crew on a test flight to the International Space Station in 2019, yes, but they would then need to undergo and pass rigorous safety tests—and the timeline for that is slipping. The companies’ contracts with NASA, established in 2014, had called for passing final certification tests in 2017. Based on a new GAO report released Wednesday, SpaceX may not get certified for regular flights to the ISS until December 2019, and Boeing until February 2020. The companies have a “considerable amount of work” to do to meet safety standards, Chaplain noted.

“Aggressive schedules and delays are not atypical for programs developing new launch vehicles or crew vehicles,” Chaplain said. “But in this case, the delays and final certification dates raise questions about whether the United States will have uninterrupted access to the space station beyond 2019.”

In between Gerstenmaier and Chaplain sat representatives for SpaceX and Boeing. Hans Koenigsmann, a SpaceX vice president, and John Mulholland, a Boeing vice president, both assured the members of Congress at the hearing that their companies would be ready to meet this demand on time.

But the GAO report suggests a different story, and Wednesday’s hearing, held by the House Subcommittee on Space, began with some sharp words from the subcommittee’s chairman about the report’s prediction of more delays.

Brian Babin, a Republican congressman from Texas, said SpaceX and Boeing are “behind schedule, may not meet safety and reliability requirements, and could even slip into cost overruns.”

“Both companies are making progress, but certainly not at the rate that was expected and not without significant challenges to safety and reliability,” Babin said. “In order to remedy these problems, NASA may seek additional funding or accept significant risks. Neither of those options is viable.”

The Commercial Crew Program has been plagued with delays since its inception. NASA’s initial target date of 2015 was pushed to 2017, and then again to mid-2018. Last week, NASA announced some more delays: Un-crewed demonstrations by both SpaceX and Boeing are now scheduled to take place in August, and crewed flights are expected to follow in November and December.

“The work completed took longer than originally planned, but many technical issues were discovered and resolved,” Gerstenmaier told the subcommittee. “This extra time that was taken in this development phase will help reduce the risk and magnitude of additional scheduled delays.”

Chaplain said SpaceX and Boeing have reported delays nine and six times, respectively, since NASA awarded them a combined $6.8 billion to work on crew transportation systems. She said both companies are currently working on addressing some safety problems. Boeing is trying to figure out how to prevent its spacecraft, the CST-100 Starliner, from tumbling during some mission-abort scenarios, which could threaten the safety of the crew. The company is also investigating the possibility that the spacecraft’s heat shield would damage the parachute system during reentry into Earth’s atmosphere. SpaceX, meanwhile, is trying to address safety concerns from NASA safety advisory boards about fueling its Dragon spacecraft while astronauts are inside.