Acting Defense Secretary Pat Shanahan is the longest-serving acting Pentagon head in American history, though he may have just cleared the final hurdle necessary to pursue an official appointment. An Inspector General (IG) investigation into the possibility Shanahan demonstrated favoritism toward his former employer while conducting official Pentagon duties has now cleared the former Boeing exec of any wrongdoing.

“The Office of Inspector General took these allegations seriously, and our 43-page report of investigation, which we released today, describes our conclusions and the facts on which they are based. The evidence showed that Acting Secretary Shanahan fully complied with his ethical obligations and ethical agreements with regard to Boeing and its competitors,” Glenn Fine, the IG official who oversaw the investigation, said in an additional statement.

In the complaint that spurred the investigation, a Washington-based group called Citizens for Responsibility and Ethics alleged Shanahan made public and private statements that disparaged the nation’s largest defense contractor, Lockheed Martin, while promoting Boeing, another large contractor that acquired a number of lucrative contracts in recent years. Lockheed Martin produces the F-35 Joint Strike Fighter, while Boeing has secured contracts for Block III upgrades for the Navy’s Super Hornets, new MQ-25 Stingray drone tankers, and of course, the controversial new F-15EX purchases that prompted a public debate about the need for more fourth-generation fighters in the era of stealth platforms like the F-35.

While none of these Boeing-acquired contracts seemed to be the result of Shanahan’s interference, the controversy regarding new F-15 purchases, in particular, seemed to coincide with accusations of Shanahan’s favoritism in the press. Now, the Pentagon’s top watchdog has cleared Shanahan of exerting any undue influence over the Department of Defense. It suggests the reasoning behind Boeing’s recent success at procuring government contracts is likely due to its aggressive efforts at catering to the Pentagon’s fiscal reluctance to delve back into an F-35-like project. Boeing’s contracts have largely focused on cost-savings and often even include set pricing, meaning the Pentagon would not be responsible for unforeseen costs that may crop up — a stark contrast when compared to the F-35’s troubled development.

Shanahan publicly welcomed the investigation, as did a number of lawmakers, including some that seemingly felt as though this investigation was a matter of due diligence, as Shanahan had no previous government experience and spent 20 years as a Boeing employee.

“In fact, it’s overdue. Boeing is a behemoth 800-pound gorilla — raising possible questions of undue influence at DOD, FAA and elsewhere,” Sen. Richard Blumenthal, a Democrat from Connecticut, said when the investigation began.

Now, with Shanahan cleared of any wrongdoing, it seems likely that President Trump will push for his official appointment as Defense Secretary, though it’s unclear how quickly Trump will move.

“I like acting. It gives me more flexibility,” Trump said in January.