(U.S. Air Force photo by Staff Sgt. Cory D. Payne)

Acting Secretary of Defense Pat Shanahan took a swipe at the F-35 Lightning II Joint Strike Fighter in a off-camera briefing at the Pentagon Jan. 29, 2019.

Shanahan, a former Boeing executive, has been accused of bias toward his former company, which lost the bid for the development of a fifth-generation stealth fighter jet to competitor Lockheed Martin.

"Am I still wearing a Boeing hat? I think that's just noise," the acting secretary said Jan. 29, 2019, responding to the allegations. But, then he took a thinly-veiled jab at the F-35.


"I'm biased towards performance. I am biased toward giving taxpayers their money's worth. The F-35 unequivocally, I can say, has a lot of opportunity for more performance," he explained, possibly suggesting that the aircraft is not quite where it needs to be.

Shanahan has signed an ethics agreement recusing himself from participating in matters pertaining to Boeing, a major US defense contractor.

An F-35 Lightning II performs aerial maneuvers during a combat power exercise at Hill Air Force Base Nov. 19, 2018.

(U.S. Air Force photo by Airman 1st Class James Kennedy)

His latest comments on the fighter, which were relatively diplomatic, are nothing compared to what he reportedly said in private meetings while serving as the deputy secretary of defense.

A former senior Defense Department official recently told Politico that Shanahan has described the F-35 as "f---ed up" and said its maker, Lockheed Martin, "doesn't know how to run a program."

"If it had gone to Boeing, it would be done much better," that same former official recalled Shanahan saying, according to Politico.

Lockheed beat out Boeing in the Joint Strike Fighter competition around the turn of the century, with the Department of Defense ultimately picking Lockheed's X-35 — which later became the F-35 — over Boeing's X-32 in 2001.

During its development, the F-35, a costly project which could cost more than $1 trillion over the course of its lifetime, has faced constant criticism for a variety of problems. The F-35 is generally considered the most expensive weapons program in US history.

A formation of F-35A Lightning IIs, from the 388th and 419th Fighter Wings, fly over the Utah Test and Training Range as part of a combat power exercise on Nov. 19, 2018.

(U.S. Air Force photo by Staff Sgt. Andrew Lee)

"The F-35 is our future," he said in September 2018 at the Air Force Association's Air, Space & Cyber Conference.

"I think we can all agree that it is a remarkable aircraft, with eye-watering capabilities critical to the high-end fight," he added. "I tip my hat to its broad team of government, industry, and international partners. Having worked on programs of similar size and complexity, I have enormous respect for your talent and commitment."

Despite these decidedly kind words, his comments Jan 29, 2019, seem to suggest that the F-35 has left a lot to be desired.

This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.