Air Force pilots in F-35A aircraft recently wrapped up the final two of 10 guided release tests to certify the jet to carry the B61-12 nuclear gravity bomb, the Air Force said Monday in a press release.

Two F-35A Lightning II aircraft, piloted by the The 422nd and 59th Test and Evaluation Squadrons, took off from Nellis Air Force Base and dropped the inert bomb mockups at Sandia National Laboratories’ Tonopah Test Range. The drops are supposed to be the last “on-aircraft testing for the initial nuclear certification effort” for F-35A, the Air Force’s variant of the jet, the service wrote in a press release

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“Due to operational security, we cannot release the exact dates of the tests,” a spokesperson for Air Force Air Combat Command wrote in an email to Defense Daily.

According to photos posted online Monday by Nellis Air Force Base, the test took place on Sept. 21.

F35-A eventually will be certified to internally carry two B6-12 gravity bombs, provided by the Department of Energy’s National Nuclear Security Administration (NNSA) with guided tail kits by Boeing [BA] that will provide what the Air Force has called a modest standoff capability for the nation’s oldest deployed nuclear weapon.

This summer, the officer in charge of the Air Force’s Nuclear Weapons Center in Albuquerque, N.M., said it might take up to a year longer than recently expected to certify F-35 to carry B61-12. According to the Air Force’s 2022 budget request, certification should be finished in fiscal year 2026. In its 2021 request, the service thought it might achieve certification in fiscal 2025.