While DoD and Lockheed Martin [LMT] hope to reach a production rate of 156 annually for the F-35 fighter, building more than 156 per year for the U.S. Air Force, Navy, and Marine Corps and foreign nations would require new tooling, Air Force acquisition chief Andrew Hunter said on Apr. 26.

“We’ve been working closely with Lockheed Martin on production capacity,” Hunter told the Senate Armed Services Committee’s airland panel in response to a question from Sen. Richard Blumenthal (D-Conn.). “Right now, they would be very stressed to produce at a rate beyond that [156 annually]…If we wanted to go to a higher production rate, we would probably have to increase tooling, and one of the significant limiters there is the center body piece.”

Northrop Grumman [NOC] builds the F-35’s center fuselage and BAE Systems the aft fuselage.

Northrop Grumman’s Palmdale, Calif. plant that builds the F-35 center fuselage is out of space for increasing F-35 production significantly above the 156 fighters planned per year. In February, Lockheed Martin said that it had signed a letter of intent with Northrop Grumman and Germany’s Rheinmetall to explore the opening of a second center fuselage assembly location in Germany.

In fiscal 2024, the Air Force requests 48 F-35As, and the service wants to sustain that rate in the next few years. DoD has been buying the tri-variant F-35 for more than 17 years–the first F-35A rolled out of Lockheed Martin’s Ft. Worth plant on Feb. 19, 2006, but DoD has yet to approve full-rate production for the fighter–an approval that could mean a rate of 80 F-35As per year for the Air Force.

U.S. allies “are a huge component of the [F-35] program,” Hunter said. “Since the conflict in Ukraine was initiated by Russia, we’ve had many additional partners and allies make the  decision to purchase the F-35.”

17 countries participate in the F-35 program, and the Czech Republic and Greece may become the newest buyers. The three latest countries to announce contract signings are Finland in February last year, Switzerland last September, and Germany last December.

Lockheed Martin plans to finish its 1,000th F-35 by the end of this year.

On Dec. 30 last year, Lockheed Martin said that the F-35 Joint Program Office and the company had finalized a Lot 15-16 contract that may be worth $30 billion to build and deliver up to 398 F-35s domestically and internationally–145 aircraft for Lot 15, 127 for Lot 16, and up to 126 for the Lot 17 contract option, including the first F-35 aircraft for Belgium, Finland and Poland (Defense Daily, Jan. 10). Those lots are to include Technology Refresh 3 (TR-3), powered by the L3Harris [LHX] integrated core processor.

F-35 program officials have described TR-3 as  the computer “backbone” for Block 4, which is to have 88 unique features and integrate 16 new weapons on the F-35, which became operational in July 2015.