The Defense Department wants to buy up to 450 F-35s in a three-year block buy beginning in 2018, a move that requires congressional approval and would let the U.S. and partner militaries begin to see savings by providing contractors with a bigger commitment to the aircraft.

Frank Kendall, defense undersecretary for acquisition, told reporters Friday following the annual F-35 CEO meeting in Oslo, Norway, that the block buy plan would drive down costs and increase fielding of the jet in both the U.S. and international community.

"It allows industry to plan with some confidence in the next few years of production," Kendall said. "As we are moving into '15, '16 and '17 we are also increasing production rates . By '18 you get to a number that makes it a lot more attractive to talk about economies of scale."

A multiyear commitment to a large number of jets would also show partner nations the benefits of committing to the program, Kendall said. The F-35 Joint Program Office is still waiting to hear whether Canada and Denmark will buy the F-35. All of the other partners expressed interest in participating in the block buy proposal, Kendall said. No total cost numbers were discussed.

In total, the Pentagon plans to purchase 2,443 of the Lockheed Martin jets, with allied purchases bringing the total number of the jets produced to more than 3,100.

Congress in its drafts of the fiscal 2016 National Defense Authorization Act is wavering on future F-35 buys for the U.S. military. The Senate Armed Services Committee, in its markup of the bill, is limiting funding for the Air Force's planned increase to $4.3 billion in 2016 until the Pentagon can certify the Air Force's schedule for initial operating capability, or can revalidate the F-35 program buy.

"There's quite a bit of time to work through the details and talk to Congress," Kendall said.

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Kendall said he has seen "good progress" in the program, with lower costs and better performance relative to the program's 2011 baseline, and it is staying close to its projections on schedule. However, any changes to the number of F-35s approved would have to require other changes to the military as a whole.

"Basically our force structure drives the number of airplanes we need," Kendall said. "Unless there's a change in force structure, the number will stay the same."

Unlike previous CEO meetings, this year's focused more on fielding the aircraft and getting to a deployable status, whereas previous meetings stressed production schedules and staying on the baseline, Kendall said.

"There's a change in the orientation of the program, from working our way through the risks associated with developmentand getting the initial products fielded, to getting confident about finishing [development] and a much more intent focus on getting to the fielding and making sure we are going to meet all the IOCs," he said.

The annual meeting includes representatives from all international partners and the services, along with industry. Next year Kendall expects to host all the parties at the first operational base, Marine Corps Air Station Yuma, Arizona, he said.

Marine Corps testing

The F-35 CEO meeting came as the U.S. Marine Corps finished a critical test of its F-35B aircraft, flying simulated operations off the deck of the amphibious warship USS Wasp. Lt. Gen. Jon Davis, the Marine Corps deputy commandant for aviation, said the Marines were able to accomplish all of their test points in the operations, which began May 18 and wrapped up May 27.

Ninety-one Marines operated on the ship, flying 108 sorties, consisting of 88.5 flight hours over eight days . Marine pilots flew training missions such as carrier qualifications, airborne interdiction and simulated support for rescuing downed aircrew, and flying against each other in force-on-force training, he said.

An MV-22 Osprey also flew an extra F135 engine to the ship , and maintainers were able to change out an engine on an aircraft, he said.

"We got what we wanted out of the shipboard period," Davis said.

Going forward, the Marine Corps expects to conduct a full operational readiness inspection of the squadron that will hit initial operating capability first by the deadline of July. Once the squadron says it is ready, the Marine Corps will conduct a 10- to 14-day inspection of maintenance and flying operations to make sure the squadron is ready for deployable status.

The level of inspection is "kind of unprecedented," Davis said, but could be the norm for all Marine Corps squadrons as they stand up.

Acting Army Secretary Robert Speer visits U.S. and partner troops at Grafenwoehr, Germany, in May. (Markus Rauchenberger/Army)

Air Force maintenance issue

The Joint Program Office and the Air Force remain confident the Air Force will reach initial operating capability with the first combat squadron of F-35As at Hill Air Force Base, Utah, despite a continued shortage of maintainers available to work on the jet.

The Air Force planned to get the bulk of the 1,100 maintenance personnel required for IOC by retiring its A-10 Thunderbolt II fleet, a move Congress blocked last year and will likely block again this year. The service has been able to get 150 personnel by moving some A-10s to its backup inventory. The Senate Armed Services Committee, in its version of the 2016 defense bill, would require the Air Force to cut back on headquarters personnel and ground 24 F-16s at Hill to free up billets for F-35 maintainers .

Maj. Gen. Jeffrey Harrigian, director of the Air Force F-35 Integration Office, said last week the service must have a plan in place by the end of summer to get the right number of personnel ready to meet IOC on time. Harrigian reiterated Friday from Oslo that the service is "on a glide path" to meeting the summer 2016 deadline and that there are no "impactful issues" to prevent meeting it.

The service already has a few of the F-35As it intends to use in its first operational squadron . Remaining aircraft are still in production, said Lt. Gen. Christopher Bogdan, the director of the F-35 Joint Program Office. All of the aircraft will require six to eight modifications at the Ogden Air Logistics Center at Hill to meet IOC with the planned software package, block 3i. The aircraft are all expected to be delivered on time, he said.