RAF FAIRFORD, England — The US Defense Department's long-awaited contract for F-35 low-rate initial production (LRIP) lots 9 and 10 is in its final stages and may be settled in time for Farnborough International Airshow next week.

"My guys are back at home right now finishing up this deal," F-35 Joint Program Executive Officer Lt. Gen. Christopher Bogdan said Saturday at the Royal International Air Tattoo (RIAT). "We think we're close enough such that my contracting officers can close this deal out."

The timing of the agreement, which will cover more than 140 aircraft valued at approximately $14 billion for US and international customers, will be up to aircraft manufacturer Lockheed Martin, Bogdan said.

"We are in the end game. We all understand what the costs are in building that many airplanes, and now it's just a matter of us working a business deal that's fair to everybody. And that's not always easy either," he said. "But we've gotten past the big rocks, so to speak. We're in the end game, and the important thing here is to now to come up with a business arrangement that's fair to everybody."

A Farnborough contract announcement would be another publicity coup for the F-35, which is making its first UK appearance at RIAT and Farnborough. The aircraft was planned to make its international debut at Farnborough two years ago, but an engine fire led to the grounding of the fleet and the cancellation of its appearance.

This year, the US Marine Corps sent three F-35Bs and the US Air Force sent F-35As to RIAT for demonstrations. Both performed Friday, and the Marine Corps' planes will also fly at Farnborough.

"It's a big deal. For many years people thought it was a paper airplane, and all they would hear about are the negative things about it," Bogdan said. "Now they have the opportunity to see the airplane fly and to watch its incredible capabilities."

The joint program office originally expected an LRIP 9 and 10 contract early this year, but Bogdan said the government needed more time to understand the full cost of the airplane.

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"It's just taken us longer to explore all of the costs all the way through the supply chain to make sure that the taxpayers are getting a good deal," he said. "And so I don't blame anybody for the delay, other than the government had to do its due diligence on $14 billion worth of work."

The Defense Department and F-35 engine manufacturer Pratt & Whitney announced a $1.5 billion agreement for F135 engines on Thursday. The company will manufacture 99 engines as part of the LRIP batch.

The program office is also eyeing a block-buy contract in fiscal 2017 for international partners and foreign military sales customers buying lot 12 jets, with US participation beginning in FY18 for lots 13 and 14 if approved by Congress.

"I think it is for sure on track for the services and the Congress to do that in '18," Bogdan said.