The inspector general for the Pentagon announced yesterday that it will be reviewing how exactly SpaceX’s rockets became certified to launch payloads for the US Air Force back in 2015, Bloomberg first reported. In a letter to Heather Wilson, the secretary of the Air Force, the inspector general, Michael Roark, wants to know if the certification process complied with the Air Force’s guidelines for certifying new launch vehicles.

The news comes nearly four years after SpaceX fought and won the ability to launch military satellites with its Falcon 9 rocket. Before this certification, the Air Force mostly relied on a sole company to launch its payloads into space: the United Launch Alliance, a joint venture between Boeing and Lockheed Martin. But SpaceX also wanted the ability to bid for national security contracts, and the company sued the Air Force in 2014 for not allowing other providers to compete for a multi-year contract worth $11 billion.

nearly four years after SpaceX fought and won the ability to launch military satellites

SpaceX settled the suit after the Air Force agreed to work with the company to certify its vehicles. The company then received approval in May 2015 to fly national security launches, and these kinds of missions have become a big part of SpaceX’s business ever since. The company just flew a new GPS satellite for the Air Force in December, and it even launched the Air Force’s secretive spaceplane, the X-37B, in 2017. SpaceX also has numerous launches lined up for the Air Force in the future, including a couple on the company’s more massive Falcon Heavy rocket. Air Force officials have even expressed interest in flying on SpaceX’s reusable rockets that have previously flown to space and back.

It’s unclear how the outcome of this new evaluation will affect any of SpaceX’s future missions, though. The inspector general’s audit will be done during February and will take place at the Space and Missile Systems Center in El Segundo, California. SpaceX did not receive a heads up about the audit and doesn’t know why it began. However, the inspector general’s office said the decision to the do the evaluation is part of a larger project of government oversight. “This was a self-initiated project by the Office of Inspector General,” Dwrena Allen, a spokesperson for the DoD inspector general, said in a statement to The Verge. “It is one of the key projects in the OIG’s expanding oversight focus on the Department of Defense’s space, missile defense, and nuclear management challenges.”

There’s been renewed focus on how the Air Force procures launches lately, thanks to a recent letter from lawmakers in California — where SpaceX is located. In early February, Sen. Dianne Feinstein (D-CA) and Rep. Ken Calvert (R-CA) wrote letter to Sec. Wilson arguing for a review of how the Air Force awards launch contracts, according to a report in Space News. The letter was in response to a recent round of contracts that the Air Force awarded in October, meant to further the development of new launch vehicles that could fly national security payloads. The awards, worth a combined $2.3 billion, went to three companies: Blue Origin, Northrop Grumman Innovation Systems, and United Launch Alliance. SpaceX was left out, despite the fact the company is developing a new massive rocket called the Starship.

Eventually, the Air Force will select at least two launch providers that can compete for national security contracts beginning in 2020. Since SpaceX is currently certified to launch military satellites, it’s still in the running, despite not receiving the October investment from the Defense Department. But in their letter, Feinstein and Calvert argued that the recent awards created an “unfair playing field,” according to Space News.

Updated February 12th, 2:55PM ET: This article was updated to include new information about SpaceX’s awareness of the audit.

Updated February 12th, 1:20PM ET: This article was updated with a statement from the Defense Department’s inspector general’s office.