The US Department of Defense and aircraft manufacturer Lockheed Martin "now have a handshake agreement" on the purchase of a first batch of 157 of the aircraft, at an 8.8 percent reduction in price compared to the previous lot of F-35As, said Ellen Lord, the Undersecretary of Defense responsible for acquisitions.

The Pentagon has also taken an option to purchase 321 aircraft over the next two years with average reductions in price of 15 percent across all models, said Lord.

If all options are exercised -- and Congress approves -- the value would be $34 billion.

"This is a historic milestone for the F-35 Enterprise, and marks the largest procurement in the history of the Department," Lord said.

The F-35A, which is operated by the US Air Force, will cost less than $80 million apiece in 2020, a year earlier than expected, she said.

According to Pentagon figures from last October, 320 F-35s had been delivered worldwide, including 245 in the US.

"This agreement symbolizes my commitment to aggressively reduce F-35 cost, incentivize industry to meet required performance, and to deliver the greatest capabilities to our warfighters at the best value to our taxpayers," Lord said.

Launched in the 1990s, the F-35 program has an estimated cost of nearly $400 billion for the Pentagon, with the goal of producing nearly 2,500 of the aircraft in the coming decades.

Including maintenance, the total cost of the F-35 program is estimated at $1.5 trillion over the life of the program, until 2070.

The announcement of the huge contract comes three days after an ultimatum from the Pentagon to Turkey, giving it until July 31 to give up the purchase of the Russian S-400 air defense system that Washington considers incompatible with participation in the F-35 program.

If Ankara has not scrapped the S-400 purchase by that date, Turkish pilots training in the United States on the F-35 will be expelled, and agreements with Turkish firms subcontracted for manufacturing the stealth warplane will be cancelled.

Proponents tout the F-35's radar-dodging stealth technology, supersonic speeds, close-air-support capabilities, airborne agility and a massive array of sensors giving pilots unparalleled access to information.

But the program has faced numerous delays, cost overruns and setbacks, including a mysterious engine fire in 2014 that led commanders to temporarily ground the planes.

sl/elm/wd/it

LOCKHEED MARTIN