The F-35 programme office has confirmed the estimated cost overrun for the first 28 production jets is roughly $1.15 billion, and not $771 million as previously reported. The higher figure includes the roughly one-third share of the overrun absorbed by Lockheed Martin and Pratt & Whitney.
The US government has to pay the remaining $771 million in extra costs under the terms of the first three lots of low-rate initial production (LRIP).
Sen John McCain first revealed the $771 million figure in a tweet on 12 July, calling the cost overrun "disgraceful".
On 13 July, Lockheed Martin tweeted that the F-35 is showing "significant progress", which drew a quick response from McCain via the same online medium.
"To most observers, a $771M cost overrun for 28 F-35s doesn't qualify as 'significant improvement.' Taxpayers deserve better," he wrote.
The dispute could set up a clash in final negotiations over the fiscal year 2012 budget. The Department of Defense has asked for another $264 million to pay the initial overage costs. If McCain succeeds in blocking the additional payment, the money would have to be found somewhere else or F-35 orders could be reduced.
The sharp exchange over Twitter over-shadowed a major news event for the F-35 programme.
© Lockheed Martin
The first F-35A conventional take-off and landing variant (above) arrived at the programme's international training hub at Eglin AFB, Florida, on 14 July. Designated AF-9, the aircraft is the first jet delivered for non-flight test purposes.