Publicly, both Boeing and SpaceX maintain that they will fly demonstration missions by the end of this year that carry astronauts to the International Space Station. This would put them on course to become certified for "operational" missions to the station in early 2019, to ensure NASA's access to the orbiting laboratory.

On Wednesday, during a congressional hearing, representatives from both companies reiterated this position. "We have high confidence in our plan," Boeing's commercial crew program manager, John Mulholland, said. SpaceX Vice President Hans Koenigsmann said his company would be ready, too.

However their testimony before the US House Subcommittee on Space was undercut by the release of a report Wednesday by the US Government Accountability Office. The lead author of that report, Christina Chaplain, told Congress during the same hearing that she anticipated these certification dates would be much later. For SpaceX, operational flights to the station were unlikely before December, 2019, and Boeing unlikely before February, 2020, Chaplain said.

This is a problem for NASA, which has the capacity to purchase rides on the Russian Soyuz vehicle through September, 2019, but thereafter has limited options. "Delays and uncertain final certification dates raise questions about whether the United States will have uninterrupted access to the International Space Station beyond 2019," the report states.

Beyond the sparks during the hearing—in which members of Congress expressed some justifiable frustration after having been informed of the new delays—the report makes for interesting reading. Indeed, its estimate of certification delays appears to rely almost entirely on information from NASA's commercial crew program manager, Kathy Lueders. This offers a rare window into what NASA really thinks the schedule for commercial crew flights is.

NASA’s frustrations

The report cites two reasons for the difference in the more optimistic estimates from Boeing and SpaceX and more pessimistic schedule from NASA: "The contractors are aggressive and use their schedule dates to motivate their teams, while NASA adds additional schedule margin for testing." In addition, "Both contractors assume an efficiency factor in getting to the crewed flight test that NASA does not factor into its analysis."

Then, there is this nugget in the report that gives us some insight into how NASA and Lueders really feel about the contractors: "The program manager added, however, that she relies on her prior experience for a better sense of schedule timeframes as opposed to relying on the contractors’ schedules." Clearly, there are some trust issues here.

Overall, the participants at the congressional hearing Wednesday agreed that the commercial crew program is still a net plus for NASA and the government. The space agency will eventually get crew services for less than it would have cost the government to develop them itself, and this federal investment will help US companies increase their already vibrant commercial activity in low-Earth orbit. However, the patience of lawmakers appears to be wearing thin with the ongoing delays.

"Both companies are making progress, but certainly not at the rate that was expected, and not without significant challenges to safety and reliability," the chairman of the subcommittee, Texas Republican Brian Babin, said in his opening statement. "In order to remedy these problems, NASA may seek additional funding or accept significant risks. Neither of those options is viable."