NATIONAL HARBOR, Md.—It will take up to 18 months to clear the full backlog of F-35s that went directly from the production line into storage, company aeronautics president Greg Ulmer told Air & Space Forces Magazine. The company did reach one noticeable milestone in July, though, delivering its 1,000th Lightning II fighter with little fanfare.

Ulmer, speaking with Air & Space Forces Magazine at AFA’s Air, Space & Cyber Conference, said he couldn’t provide the specific rate at which Lockheed is delivering its stored F-35s, but said “it’s going well. It’s going to take us 12-18 months to get those aircraft and [the] backlog out.”

Eighteen months is longer than the Government Accountability Office estimated in May. The sequence of delivery has been approved by the users, Ulmer said.

Lockheed has declined to say exactly how many F-35s went into storage during the delivery pause, but it is likely 100 or so. One of them had the distinction of becoming the 1,000th delivery when it was sent to the 115th Fighter Wing of the Air National Guard at Truax Field, Wisc., in July.

Unlike previous milestones like the 100th F-35 produced or the 100th F-35 delivered to the Air Force, there was no public announcement or ceremony at the time. Lockheed Martin’s Director of Operations Frank A. St. John noted that 1,000 fighters had been delivered in an interview with CNBC, but did not say where it had gone.

The 1,000th airframe delivered was not necessarily the 1,000th produced. The fighters are not being delivered in the order that they were built, Ulmer said, but are being mixed with deliveries of fresh-off-the-line airplanes. This approach causes “less disruption” to the factory routine of building, testing, and delivering the jets.

“We don’t want to disrupt the flow,” he said.

When they went to storage, the jets weren’t sealed up and simply parked, Ulmer said. Typically, each jet receives four checks when it rolls out of the factory; two each by Lockheed and two each by the customer. When the stored jets were completed, they got one check each from the company and the customer, and only need one more check each, Ulmer said.

“They were in warm storage” with occasional power-ons, he said. “It’s not like we weren’t taking care of those airplanes.”

The Joint Program Office “asked us to help inform them of what the most efficient unwind” would be, he said, and then the JPO worked with the services and foreign customers to set the sequence of deliveries.

“There are, you can imagine, milestones out there of significance for different customers,” Ulmer said. Some countries are getting their initial jets, such as Poland and Belgium, while “Australia is pursuing full operational capability, and they needed their full complement of aircraft. … So these are the kinds of priorities that define who got what capability, when.”

He added that he’s heard no complaints from customers about the sequence of deliveries.

All the jets that go out the door—or deliver from the storage area—are loaded with the Tech Refresh 3 hardware, “and they’ll all get the TR-3 software inserted before they deliver,” he said.

The yearlong hold on deliveries was due to the fact that jets were built with TR-3—faster processors, a new display and other improvements—but the TR-3 package had not yet been fully tested, and the government declined to accept the jets with it. The JPO now expects that full TR-3 testing will be finished in 2025.

Ulmer declined to be more specific as to when in 2025 that will happen because “there are still things you could find in discovery” during testing.

As a stopgap—because both U.S. and partner countries needed to receive new airplanes to conduct training and have combat capability—JPO director Lt. Gen. Michael Schmidt in July approved deliveries with a “truncated” version of the TR-3 software, so handovers could resume and pilots could train with the new version of the aircraft. The truncated version allows training with many of the systems and weapons that will be in future jets.

Ulmer said he disliked the term “truncated” and prefers “full combat-capable training software release.”

Schmidt took his time approving the release, as he was waiting for a version that was more stable in flight and needed fewer reboots per sortie. Several new versions of the software have been issued since July, giving the aircraft what the JPO calls a “more robust training capability.”

In a May report, the GAO estimated it would take a year to deliver the stored F-35s alongside the new ones, for while Lockheed told the government it could deliver 20 per month—one every business day, roughly—the GAO noted that the company had never done better than 13 per month.

“Even at this faster rate, delivering the parked aircraft will take about a year once the TR-3 software has been completed and certified,” the GAO said. The watchdog agency reported, though, that the Defense Contract Management Agency deemed the 20 per month figure “feasible,” though it also said that rate would stress the workforce needed to accomplish the deliveries and lead to “coordination challenges” with the government.

Each aircraft being delivered is “a full-up-round,” Ulmer said, with all the TR-3 enhancements, including the updated Digital Aperture System hardware, which provides 360-degree all-weather and night visibility on the pilot’s helmet visor.

The version being delivered has “90-95 percent of the full capability in it,” he asserted. “It has much of the weapons capability in it. … We just need to get through the flight test and the certification air worthiness associated with those capabilities out of flight test and then into our customers hands.”  

Ulmer predicted that the delivery total for F-35s in calendar 2024 will be 75-110 jets—as planned, and then “next year, I’ll say, 156-plus.” That’s the number predicted by the company three years ago.

“I told you, we didn’t slow the production system down. International demand is very strong,” he said, noting the latest buy of 32 airplanes from Romania.

“And I think you’ll see a lot of international, existing customers, increasing their program of record. So I see us running at 156-plus. Because we have a backlog.”

He cautioned that all of these estimates are subject to “external factors and things you don’t have control over,” like bad weather, which could delay the TR-3 test program. But “we’re not going to cut a corner. I call it ‘build slow to go fast.’ We have to have certified pilots. We have to have chase aircraft. You have to have the weather until you get IFR clearance. So we’ll follow all the rules and go as fast and as safely as we can.”