WASHINGTON — A group of mostly Republican lawmakers, many from states with a United Launch Alliance presence, want to know how tough NASA and the U.S. Air Force are getting with SpaceX after a June 28 launch failure of the latter’s Falcon 9 rocket that destroyed a load of NASA cargo bound for the International Space Station.

Although the mission was one of a dozen SpaceX took on as part its Commercial Resupply Services contract with NASA, the space agency legally had no oversight of the commercially procured launch, which was licensed by the Federal Aviation Administration.

As is typical with commercial launches, SpaceX is in charge of the mishap investigation, the initial results of which indicate that a faulty strut caused the rocket to disintegrate some 2 minutes after liftoff from Cape Canaveral Air Force Station in Florida. The Falcon 9, heavily booked with a mix of commercial missions, mostly for NASA and satellite operators, probably will not return to flight earlier than September, SpaceX founder and Chief Executive Elon Musk said in July.

SpaceX’s lead role in the investigation has left 17 U.S. representatives with “serious reservations” about “whether the investigation and engineering rigor applied will be sufficient to prevent future military launch mishaps.” So says a July 30 letter the group sent to NASA Administrator Charles Bolden and Air Force Secretary Deborah James.

The Falcon 9 recently was certified to launch Air Force missions, positioning SpaceX to compete in a market that Denver-based ULA has long had to itself. The first of the competitive launches, of a GPS 3 satellite, is slated for award this year.

The lawmakers wanted to know whether the accident would affect Falcon 9’s hard-won certification.

So far, it has not.

“At this time, the Falcon 9 Launch System remains certified and eligible to compete for future national security space launch missions,” Lt. Gen. Sam Greaves, commander of the Air Force’s Space and Missile Systems Center at Los Angeles Air Force Base in California, said in an Aug. 4 statement. However, the Air Force “has the authority to maintain certification or require some flight worthiness activities to be re-accomplished.”

More than half of the lawmakers who signed the letter hail from states where ULA or its business partners have a presence, including Colorado and Alabama. Only two were Democrats.

SpaceX’s government affairs department quickly fired back in an email blast to lawmakers, a copy of which was obtained by SpaceNews.

“The SpaceX led investigation into the CRS-7 mishap has followed the law and processes established with the FAA and our customer, NASA, with direct involvement of the Air Force; it is inaccurate to suggest that the investigation has been non-standard in any way,” the SpaceX email reads.

Greaves apparently agrees with SpaceX on that point.

“I have no concern at all with the process that is being used by SpaceX to conduct the investigation,” Greaves said during a July 31 breakfast here sponsored by the Mitchell Institute. “We treat SpaceX exactly how we treat ULA. There should be no perception SpaceX is getting a pass or that we treat them any differently.”

SpaceX’s email also notes that company-led investigations are standard operating procedure when it comes to launch “mishaps,” which are legally distinct from launch “accidents” under U.S. federal law. A mishap, SpaceX said in its legalese-laden communique, involves “no third-party loss, no flight line deviation, and no loss of life.”

Both the SpaceX failure and the Oct. 28 failure of Orbital ATK’s Antares vehicle during one of the latter company’s NASA Commercial Resupply Services missions legally fit that description of “mishap,” according to the SpaceX letter. Orbital ATK is leading the Antares investigation, which is slated to wrap up any day.

NASA appears to agree with SpaceX’s appraisal of the situation.

“NASA has received the letter and looks forward to reviewing it,” NASA spokeswoman Tabitha Thompson wrote in an Aug. 4 email. “Under the authority of the Federal Aviation Administration (FAA) which licensed the launch, and per FAA regulations, SpaceX is leading its mishap investigation, as Orbital ATK is leading the investigation into its October 2014 mishap, both with FAA oversight. NASA is participating in both efforts and is confident both companies will understand the specifics of their respective mishaps, learn from them, and correct the issues so they can return to flight.”

SpaceX spokesman John Taylor referred questions about the lawmakers’ letter and the company’s response to the Air Force.

The complete list of lawmakers who signed the July 30 letter follows, in the order their signatures appeared.

Rep. Mike Coffman (R-Colo.)

Rep. Randy Forbes (R-Va.)

Rep. Robert Aderholt (R-Ala.)

Rep. Rob Bishop (R-Utah)

Rep. Mo Brooks (R-Ala.)

Rep. Ken Buck (R-Colo.)

Rep. Bradley Byrne (R-Ala.)

Rep. Tom Cole (R-Okla.)

Rep. Denny Heck (D-Wash.)

Rep. Jody Hice (R-Ga.)

Rep. Doug Lamborn (R-Colo.)

Rep. Martha Roby (R-Ala.)

Rep. Terri Sewell (D-Ala.)

Rep Scott Tipton (R-Colo.)

Rep. John Flemming (R-La.)

Rep. Gary Palmer (R-Ala.)

Rep. David Jolly (R-Fla.)

Mike Gruss contributed to this story from Washington.