The Air Force expects to certify the F-35 Joint Strike Fighter to carry nuclear weapons in January, once sufficient numbers of pilots and ground crew are trained to carry out the mission.

But it may not have the jets, equipped with the proper avionics and mission systems, needed to perform the nuclear mission until several months later, according to a new delivery schedule F-35 manufacturer Lockheed Martin described in a filing this summer with the Securities and Exchange Commission earlier this month.

Dual-capable F-35As, which can carry both conventional munitions and a version of the B61 nuclear bomb, are expected to reach “operational certification” in January, Ann Stefanek, the chief spokesperson for the Secretary of the Air Force, told sister publication Exchange Monitor on Wednesday. The Air Force approved initial nuclear certification for the jet itself in September 2022.

“The aircraft is already certified,” Stefanek said in an email. “Operational certification refers to personnel being certified to carry out the mission.”

Lockheed Martin [LMT] recently updated its schedule for the jets that will have the necessary equipment upgrade package that enables internal carriage of two B61-12 bombs, among other capabilities.

The bomb will be a homogenized version of Cold War-era four variants of the B-61, the oldest active weapon in the U.S. nuclear arsenal. The B61-12 will extend the life of the bomb for another 20 years and replace all previous variants except the B61-11, which will remain in the stockpile.

The National Nuclear Security Administration is responsible for certifying the bomb itself before delivering them to the Air Force.

To carry the bomb, the F-35A needs what the Air Force has dubbed “Technical Refresh 3,” or TR3, the equipment and software upgrade package that is the backbone of the Block 4 version of the aircraft. Lockheed now expects to begin delivering TR3 aircraft between April and June 2024, according to the SEC filing.

“As a result, we now expect to deliver 97 aircraft in 2023 (all in the TR-2 configuration), which we do not currently anticipate will impact our 2023 financial outlook,” Lockheed said.

“We are producing F-35s at a rate of 156 per year and expect to continue at that pace while simultaneously working to finalize TR-3 software development and testing. We remain focused on receiving the necessary hardware from our suppliers to deliver this critical combat capability for the F-35,” Lockheed said in the filing. “The number of 2024 F-35 deliveries will depend on when the first TR-3 aircraft is delivered and the time needed to complete the customer’s acceptance process. We continue to assess impacts to 2024 and will have updates as the test plan continues.”

A Lockheed spokesperson did not respond to a request for comment for this story.

This story first appeared in Defense Daily affiliate publication Weapons Complex Morning Briefing.