The Pentagon Inspector General concluded this week that Acting Defense Secretary Pat Shanahan did not seek preferential treatment for his former employer, Boeing, while serving at the Pentagon.

“We did not substantiate any of the allegations. We determined that Mr. Shanahan fully complied with his ethics agreements and his ethical obligations regarding Boeing and its competitors,” the inspector general said in a statement on Thursday.

The statement said Shanahan and 33 witnesses were interviewed under oath, and more than 5,600 pages of unclassified documents and approximately 1,700 pages of classified documents were reviewed.

The investigation’s favorable conclusion now clears the way for Shanahan to be nominated as defense secretary, after serving in the acting role since former Defense Secretary Jim Mattis’ departure in December.

Progressive watchdog group Citizens for Responsibility and Ethics in Washington (CREW) last month filed a complaint against Shanahan, based on media reports where anonymous sources claimed he was promoting Boeing and disparaging competitors.

Shanahan told senators at an Armed Services Committee hearing last month that he supported the investigation, and told Breitbart News after the hearing that he was not worried.

“I’m not worried. There’s not just a straight line — I’ve played way back from the line. And I welcome their work, it should be pretty straightforward,” he said.

Pentagon officials at the time refuted reports Shanahan had given Boeing preferential treatment, noting that he signed an ethics agreement that recused him from participating in matters involving Boeing.

Shanahan, 56, worked for Boeing for more than 30 years before becoming deputy defense secretary in July 2017. He last served at Boeing as senior vice president of supply chain and operations, overseeing the company’s manufacturing operations.

He is known among aviation experts as a problem solver, and is credited with almost single-handedly saving Boeing’s 787 Dreamliner about a decade ago.

Shanahan appears to be the leading candidate to permanently replace former Defense Secretary Jim Mattis, who resigned late last year. He served for 17 months as Mattis’ deputy, often sitting in for him during meetings in Washington while he was traveling abroad.

Shanahan forged a good relationship with President Trump and the White House during his work establishing the Space Force.