The F-35 production line seen from crane monorail at Lockheed Martin Plant 4, 1 Lockheed Boulevard, Fort Worth, Texas. Chris Hanoch/Lockheed Martin
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Strategy & Policy: Even as New Jets Remain Parked, the F-35 Program Hits New Milestones

March 28, 2024

The 1,000th F-35 rolled off the assembly line late this winter. It was a major program point of arrival, but there was no gala rollout for VIPs and press at Lockheed Martin’s Fort Worth, Texas, plant to mark the milestone. 

There wasn’t even a mention.

The reason: While Lockheed continues to produce F-35s, they’re being built with the Tech Refresh 3 (TR-3) hardware and software, which has yet to be proven out in flight test. The government won’t accept them until that testing concludes, so the completed jets are piling up at an undisclosed location. Some 70 or so airplanes are waiting to fly off to their operational units, but the 1,000th jet, though complete, remains undelivered. 

Despite that situation, the Pentagon cleared the F-35 for full-rate production in March—something of a formality since the enterprise is already operating at capacity—but one that paves the way for money-saving multiyear orders. 

Lockheed and the F-35 Joint Program Office (JPO) said last year that the TR-3, essentially a massive processor and software modernization on which the F-35 Block 4 and later upgrades depend, would clear testing in “mid-2024.” But in January, Lockheed CEO Jim Taiclet reported in a quarterly earnings call that “we now believe that the third quarter may be a more likely scenario for TR-3 software acceptance.”  

Taiclet said he expects between 75 and 110 F-35s will actually be delivered in calendar 2024, versus a goal of 156.

Milestone C

“Full-rate production” represents official recognition that the Block 3 F-35 has satisfactorily completed development and initial operational testing. Also known as “Milestone C,“ this status empowers the JPO to negotiate multiyear procurement of the F-35.

The F-35 program has “control of the manufacturing process, acceptable performance and reliability, and the establishment of adequate sustainment and support systems,” according to a Defense Department press release.

The F-35 is “stable and agile, and … all statutory and regulatory requirements have been appropriately addressed,” Pentagon acquisition and sustainment executive William LaPlante said in the release. He called the fighter the “premiere system that drives interoperability with our allies and partners,” and is “well-positioned to efficiently produce and deliver.”

LaPlante said there’s been “significant improvement” in the program over the last decade, and  program leaders can now “focus on the future of the F-35, instead of the past.”

Some issues remain, said Raymond O’Toole Jr., the Pentagon’s acting director of test and evaluation. The program still needs to improve the test infrastructure and ensure its “readiness to test …the upcoming Block 4 capabilities.”

Multiyear procurement should enable Lockheed to get better prices from its suppliers by giving them greater certainty about future orders so they can buy materials in economic quantities. The savings should pass on to the U.S. taxpayer. 

International F-35 partners, unconstrained by U.S. acquisition milestones, have already begun making what the JPO calls “block buys” of the fighter. Production Lots 18 and 19 are already being negotiated, but Lot 20 is likely to be the first in which the U.S. will benefit from the full-rate declaration.  

Programs historically hit Milestone C at about the seven-year point, but for the F-35, it took 23 years.

The delays in approving Milestone C over that period ranged from production challenges and testing deficiencies to software and maintainability issues. The final hurdle was integrating the F-35 into the Pentagon’s Joint Simulation Environment, a wargaming system that helps planners find the numerical sweet spot for every combat platform in terms of force size and weapons for a given conflict scenario.

But Milestone C is in many ways moot: Lockheed and its partners are already effectively at full-rate production. The company said its factory, tooling, and workforce is sized to make 156 jets a year. That number flattens the ups and downs of U.S. and foreign orders to a steady production tempo. Building faster would require more workers, tooling and expense, and that would risk intermittent layoffs, should orders decline between peaks.

Still, Lockheed has yet to build 156 F-35s in a single year. It expects to by 2026, and to then hold steady at that number for five years, according to Greg Ulmer, Lockheed’s executive vice president for aeronautics. 

In a press statement, Lockheed said it was pleased with the full-rate decision, but acknowledged “production can vary from delivered jets.” Milestone C does not affect [the production] rate but is an important milestone in a program’s maturity.”

How Many Jets in 2025?

When the Air Force released its fiscal 2025 budget request in March, the number of  Air Force F-35s included was just 42, down from the 48 it had planned to acquire in last year’s Future Years Defense Program (FYDP). The Navy and Marine Corps also reduced their appetite—the Navy from 16 to nine, the Marines from 16 to 13—so, all told, U.S. purchases would be just 68 aircraft in 2025, rather than 83.

Pentagon officials said that since Lockheed won’t deliver all the F-35s it planned to this year, the services could “defer” funding for some jets to later budgets. Acting Air Force Undersecretary Kristyn Jones told reporters the Air Force remains committed to its program objective of 1,763 F-35s.

“We want the planes that we want,” Jones said. “And the TR-3 Block 4 capabilities have been delayed. So, our approach to minimize the impact of that [is] by procuring fewer of those in the first years of the FYDP. And then, as you’ll see from our more detailed budget exhibits, that we will start to come back toward the end of the FYDP, hopefully, with all those capabilities that we need in place.”

Under this budget plan, the Air Force would acquire 42 aircraft in both fiscal ‘25 and ’26, followed by 47 each in ’27 and ’28, and 48 in fiscal ’29. By then, the program will be halfway to its numerical goal, with 946 jets left to go of the 1,763 aircraft planned. 

That obvious slowdown goes beyond the Block 4 delay. Air Force Secretary Frank Kendall told reporters he didn’t want to make the reductions, but was forced to by the Fiscal Responsibility Act, which compelled the service to find 2 percent in cuts after the ’25 budget was already built. He chose to preserve research and development for future programs over buying systems already in production. Trade-off, Kendall said, between “the mid-term force” and “the longer-term force.

“What we’re doing, essentially … is buying options for people to procure things in the future,” he said. Research and development of upcoming capabilities, like the Next-Generation Air Dominance fighter or the Collaborative Combat Aircraft (CCA), “doesn’t give you anything immediately, it gives you an option to then exercise for production later,” he said. He wants future administrations to have a choice between building new things or more older things. 

Pain Now 

The delay in getting new F-35s is “hurting already,” Kendall said. “We really need [the TR-3 and Block 4 upgrades]  “to stay competitive” with China, he stated at a March defense conference.  

“We’re going to need them in quantity, so getting on with that is really important to us.”

Not getting new jets upsets the timetable for retiring older aircraft, which “affects cost,” he said.

Jets bound for retirement like the A-10 and F-16 will have to be retained “for longer than we had planned,” Kendall explained, and this adds expenses for maintenance and training, and disrupts the transition of pilots and maintainers to the new aircraft.  

But it’s “the operational capability impact” that’s most significant, he said, because the F-35 offers such a leap in capability beyond the fighters it’s replacing. 

The JPO said the F-35 partners have considered accepting jets with “truncated” capability, something less than the full TR-3. But as of mid-March, no decision had been made.

Kendall said his prior business relationship with Northrop Grumman, which makes the Block 4 AN/APG-85 radar, means he must be recused from such decisions, and that he’d deferred that call to Joint Chiefs Chairman Gen. Charles Q. Brown Jr.

“It’s a judgment call,” according to Kendall, though his instinct would be “to hold industry responsible for delivering what they promised.” But while he would prefer “to not accept” a lesser capability, the operational argument has merit, he said. 

Ulmer said flight testing is showing “improved performance” of the TR-3, with better software stability and “significant” new weapons capabilities. He left it to the JPO to decide “what the deliverable release will be,” and said Lockheed will “align” to its decision.

Nuclear Lightnings

One other major milestone that came to light in March is that the F-35A is now certified to carry the B61-12 nuclear weapon. 

The declaration, made in October but only acknowledged in March, makes the F-35 the first fifth-generation aircraft to be declared nuclear-capable since the B-2 bomber, some 30 years ago, and marks the climax of more than 10 years of effort involving 16 government agencies, a JPO spokesman said. 

The U.S. and NATO now have “a critical capability that supports U.S. extended deterrence,” the spokesman asserted. The B61-12 has an estimated yield of 50 kilotons.

Joining the U.S. in the nuclear mission will be Germany, Belgium and the Netherlands, all of which have or will have F-35As. 

All USAF F-35As are eventually expected to have the necessary wiring and software to deploy the B61-12, but for now, only certain units are so equipped; neither the TR-3 nor Block 4 are required to deploy it. The Air Force will not identify which units will have that capability. However, Air Force squadrons at RAF Lakenheath, U.K., have been assigned the nuclear mission in the past and nuclear-certified weapons igloos are already there.

Into the Future 

With F-35A purchases as slow as they are, and newer technologies emerging, few expect the Air Force to ever acquire the full 1,763 F-35As originally planned. When that goal was set, early in the program, China was not yet viewed as a peer military competitor.  Given that the Air Force is now well along with the Next-Generation Air Dominance fighter and its “family of systems,” which includes plans for “thousands” of Collaborative Combat Aircraft, the F-35 may never get close to its objective force. 

At 48 aircraft a year, it would take more than 20 years to get there, and the design is already 25 years old. The CCA will also be far less costly; according to Kendall, it will cost only a third as much as an F-35. 

That said, Mitchell Institute for Aerospace Studies’ Heather Penney noted that in a series of recent wargames, CCAs proved “most effective” when “paired with crewed fighters.” Time and budgets will tell.