On Wednesday, a senior executive with United Launch Alliance said the US military "bent over backwards" to favor the Colorado-based rocket company in the bidding process for national security payload launches. On Thursday, Sen. John McCain (R-Ariz.), chairman of the Committee on Armed Services, asked Secretary of Defense Ash Carter to investigate these comments.

"Let me just say that yesterday disturbing statements made by a senior executive of the United Launch Alliance were reported in the media," McCain said at the onset of a committee hearing Thursday morning. "These statements raise troubling questions about the nature of the relationship between the Department of Defense and ULA. This committee treats with the utmost seriousness and implication that the department showed favoritism to a major defense contractor or that efforts have been made to silence members of congress. Mr. Secretary, I expect that you will make a full investigation into these statements and take action wherever appropriate."

McCain was referring to comments made by Brett Tobey, a vice president of engineering for United Launch Alliance, during a seminar with students at the University of Colorado-Boulder. Tobey has since resigned, effective immediately, and ULA chief executive Tory Bruno has said Tobey's comments were "inaccurate."

Tobey's statements were nevertheless potentially damning for ULA in its competition with SpaceX to win contracts from the Air Force and other branches of the military to launch national security payloads. Tobey said ULA couldn't compete on price when the Air Force sought a launch provider in 2015 for a GPS 3 satellite. "ULA opted to not bid that," Tobey said. "The government was not happy with us not bidding that contract because they felt that they had bent over backwards to lean the fill to our advantage. But... we saw it as a cost shootout between us and SpaceX. So now we're going to have to figure out how to bid these things at a much lower cost."

SpaceX sued the Air Force in 2014 because the company did not feel the military was fair and transparent in its bidding procedures for launching spy satellites and other payloads. The suit was dropped last year after the Air Force certified the company's Falcon 9 rocket for military launches. SpaceX officials declined to comment on the new dust-up.