The F-35 Joint Strike Fighter program -- already the most expensive defense acquisition program in U.S. history -- just got even more costly, to the tune of $771 million.
The Pentagon informed the Senate Armed Services Committee Monday that the first 28 production models of the F-35, some of the world's most technologically advanced fighters developed by defense contracting giant Lockheed Martin, were going to cost the additional three quarters of a $1 billion, and the government will be picking up part of the tab.
The news sparked a brief Twitter spat between Sen. John McCain, the senior Republican on the Senate Armed Services Committee and longtime critic of the F-35's cost overruns, and Lockheed Martin.
"Congress notified that first F-35 jets have cost overruns of $771M. Outrageous!" McCain tweeted Tuesday. "Pentagon asking for $264M down payment now. Disgraceful."
The next day, a tweet from Lockheed Martin said, "The F-35 team is focused on reducing costs of the jets and is showing significant improvement in key areas," and linked to recent Senate testimony by Tom Burbage, Lockheed Martin's executive VP and general manager of the F-35 program.
McCain responded just hours later by directing his next tweet at Lockheed Martin: "To most observers, a $771M cost overrun for 28 F-35s doesn't qualify as 'significant improvement.' Taxpayers deserve better."
A member of McCain's staff told ABC News that while the Pentagon has hinted at a significant new round of cost overruns for the F-35, Monday was the first time a hard figure was given for the total scope of the problem. In late June, the Pentagon filed a request to transfer $264 million from other programs to help pay for it, the staff member said.
Lockheed Martin said the additional cost was due to "inefficiencies" related to a 2004 redesign that was meant to shave thousands of pounds of excess weight from the plane and said that at this phase in production Lockheed shares the cost overruns with the government.
Throughout its production, the F-35 has been wracked with unexpected cost overruns and production delays to the point that a recent report by the Government Accountability Office said the cost of purchasing and maintaining each plane has approximately doubled from original projections by Lockheed Martin. The GAO estimates U.S. taxpayers will invest a total of $385 billion to develop and maintain 2,457 planes through 2035. The program has also come under fire for the initial inclusion of a duplicate engine development program that the Pentagon said was unnecessary.
It's not the first time McCain has publicly decried what he called "out-of-control cost overruns" by the F-35 program. In June, he proposed an amendment that would saddle Lockheed Martin with the burden of any cost overruns in the latest group of F-35s still under development.
"If we fail to act now, continuing cost overruns on the F-35 of the kind we have experienced over the last 10 years will siphon off precious resources and put at risk every other major Defense procurement program," McCain said then.
Lockheed said they have learned as the program has grown and later batches of the planes will be made more efficiently and affordably.
"Our factory performance metrics are now showing significant improvement in all key areas, we are experiencing excellent learning curve reductions in assembly hours and we have essentially eliminated all traveled work," the company said.
Representatives for the Department of Defense's joint F-35 program did not respond to requests for comment on this report.