A government watchdog group has asked the Department of Defense Inspector General to investigate whether Acting Secretary of Defense Patrick Shanahan violated ethics rules by promoting Boeing weapons systems while serving as a government official.

Shanahan, 56, worked at Boeing for more than 30 years prior to being tapped by President Donald Trump to serve as deputy secretary of defense under former Defense Secretary Jim Mattis. When Mattis submitted his resignation in December, Shanahan was named by Trump as acting defense secretary.

Since coming to the Pentagon, Shanahan has faced criticism over reports that he has touted Boeing’s line of aircraft over rival Lockheed Martin. In the fiscal year 2020 budget released Tuesday, the Air Force is set to purchase up to 80 F-15Xs over the next five years — a system, made by Boeing, that the Air Force has said it does not want.

Air Force Secretary Heather Wilson told Defense News in February that the “budget proposal that we initially submitted did not include additional fourth-generation aircraft.”

Wilson’s comments confirmed reporting by Defense News and other outlets, which have reported that the decision to buy new F-15X aircraft was essentially forced upon the Air Force. According to sources, the Pentagon’s Cost Assessment and Program Evaluation Office was a key backer of the F-15X and was able to garner the support of the Office of the Secretary of Defense.

Last week, Wilson announced that she was stepping down as Air Force secretary to become president of the University of Texas-El Paso.

Previous news reports indicated that Shanahan has disparaged Lockheed Martin’s fighter, the F-35, and other Lockheed weapons systems in private Pentagon meetings. In January Politico reported that Shanahan called the F-35 “f---ed up” and reportedly said Lockheed “doesn’t know how to run a program.”

“Mr. Shanahan appears to have participated in the decision to include more than $1 billion in federal funds in the 2020 budget cycle for the F-15X fighter aircraft,” the Citizens for Responsibility and Ethics in Washington said in their ethics complaint. “Mr. Shanahan’s reported conduct and comments appear to violate federal regulations and his Ethics Pledge, and CREW therefore requests that you investigate his alleged conduct.”

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Shanahan’s spokesman, Army Lt. Col. Joseph Buccino, said in a statement that “Secretary Shanahan has at all times remained committed to complying his Ethics Agreement, which screens Boeing matters to another DoD official and ensures no potential for a conflict of interest with Boeing on any matter."

The questions over Shanahan, who could be nominated by Trump as early as this week to serve officially as the Pentagon’s defense secretary, come as Boeing faces international scrutiny over its commercial passenger jet, the Boeing 737 Max-8. Shanahan’s last position at Boeing prior to coming to the Pentagon was at Boeing Commercial Airplanes, “where he served as senior vice president of Airplane Programs and oversaw the management of profit and loss for the 737, 747, 767, 777 and 787 programs,” the Pentagon said in 2017, when announcing his nomination.

Prior to leading the commercial airplane division, Shanahan oversaw Boeing Missile Defense Systems and was “vice president and general manager for Rotorcraft Systems in Philadelphia, where he was responsible for all U.S. Army Aviation, including the Bell-Boeing V-22 Osprey tiltrotor, the CH-47 Chinook and the AH-64D Apache attack helicopter,” DoD said at the time.

I just asked @ActingSecDef- a former Boeing executive for 20 years!- if he thought Americans are safe to fly on the type of Boeing planes that have recently crashed: pic.twitter.com/PNYDOunmK6 — Elizabeth Landers (@ElizLanders) March 12, 2019

Shanahan was asked by CNN Tuesday about the MAX-8 crashes, and said “let’s let the FAA and others take command of the situation.”

The jet has been involved in two fatal crashes over the last five months, killing more than 300 passengers and crew, and it faces a worldwide grounding in dozens of countries. It is still flying in the U.S.

Defense News air warfare reporter Valerie Insinna contributed to this report.