The Defense Department's inspector general found 719 "issues" with the F-35's primary builder, Lockheed Martin, and dive other major contractors involved in producing what became the most expensive weapons system in history, ABC News reported.
The 126-page report concludes the problems should have been caught by the $400 billion program's military overseers, the network said.
The report faults the F-35 Joint Program Office, tasked with getting the planes airborne for three U.S. military branches, for not ensuring "Lockheed Martin and its subcontractors were applying rigor to design, manufacturing, and quality assurance."
Lockheed Martin and the F-35 Joint Program Office said the issues have already been addressed for the most part.
But the inspector general's report describes problems such as "uncontrolled or unapproved" design changes in production planning, contractor personnel who didn't follow written manufacturing and assembly process instructions, inadequate calibration management systems that could hinder testing and employees with expired certifications for critical tasks, ABC said.
The report concluded the flaws "could adversely affect aircraft performance, reliability, maintainability and ultimately program cost."