Lockheed Martin chief executive James Taiclet has warned of another potential schedule slip for the F-35 programme’s Technical Refresh 3 (TR-3) activity, as shipments of the fifth-generation type fell below triple figures last year.

Delays to the TR-3 testing process in 2023 prompted the US Department of Defense (DoD) to refuse taking delivery of jets built to the new operating standard.

The airframer had previously said it expected the issue to be resolved between April and June 2024, but during an earnings call on 23 January, Taiclet indicated that this could slip further.

F-35A TR-3 test flight

Source: US Air Force

The F-35’s TR-3 software is currently undergoing flight-testing

“The second-quarter customer acceptance of delivery software remains our target,” he says. “However, we now believe that the third-quarter may be a more likely scenario for TR-3 software acceptance.

“Over 90% of the TR-3 functionality is currently in flight-test, and we are further advancing the software integration to include additional aircraft and mission subsystems,” Taiclet says.

“While this system maturation process continues to advance, it is taking somewhat more time than we originally anticipated. We are taking the time and attention to get this technology insertion right the first time, because it will be absolutely worth it.”

The DoD’s stance had a significant impact on Lockheed’s F-35 business performance in 2023, with the company ending the year having delivered 98 of the fifth-generation fighters, including 18 TR-2-standard examples during the final quarter. It had handed over 141 of the aircraft in 2022, and originally planned to increase this to between 147 and 153 last year.

While the TR-3 matter awaits resolution, Lockheed has maintained its planned production rate, with completed TR-3 aircraft being kept in storage.

Taiclet says output will continue at the current rate, but that Lockheed’s expected delivery range for 2024 “is between 75 and 110” aircraft. This means that it could end the year with between 100 and 120 built jets still awaiting acceptance.

“We feel pretty confident in where we are through the third quarter,” says chief financial officer Jay Malave. “If there were any delays beyond that, we would have to revisit our production cadence at that point in time.”

Encouraging “full transparency”, Taiclet says: “You’ve got to be honest about the schedule. What can industry do? What can the test and evaluation community handle? And what’s the supply chain capacity?

“We have to be brutally honest as an industry and with our suppliers, input that to the government and say what is feasible to keep the production rate up. We cannot afford to be over-optimistic in the ability to deliver these technologies as rapidly as one might like: there are real technical and physical challenges to doing this.

“Our commitment to the government, to the service chiefs and our allies is: I will tell you honestly what we think industry can do with the jet, and if you want to push it beyond that, I’ll tell you what the risks are and what the cost might be to do it. But let’s agree on a feasible, executable plan.”

Taiclet notes that international demand for the F-35 remains strong, with fourth-quarter highlights having included South Korea announcing a 20-unit follow-on purchase. The company also delivered a first example of the type produced for Belgium.

Meanwhile, Lockheed in 2023 delivered the first five F-16 Block 70 fighters from its Greenville assembly site in South Carolina, with output to increase significantly this year. Recipients were Bahrain (3) and Slovakia (2).

“We would expect that to triple, potentially quadruple in 2024,” Malave says. “The ramp [up] is certainly in full force: we had over 30 aircraft in WIP [work in progress] as we ended the year. The production cadence is all trending well.”