WASHINGTON — The B61-12 nuclear gravity bomb has completed its final design review, setting up production for March of 2020, the National Nuclear Security Administration has announced.

The B61-12 life-extension program consolidates and replaces the older B61-3, -4, -7 and -10 variants, in a move that proponents say will both update aging parts of the weapons and drive down upkeep costs. The review, which involved a team of 12 independent experts studying three years of data, certified that the B61-12 design meets Defense Department standards.

The weapon is certified for both the B-52 and B-2 bombers, America’s F-15, F-16 and F/A-18 fighter aircraft, and British and German Tornado aircraft under a NATO agreement. The F-35 is also planned to go through certification on the weapon at some point in the next decade.

Production qualification activities at the agency’s Pantex plant near Amarillo, Texas, will begin in October 2018, with the program on track for its first production unit in March 2020, according to an agency timeline. The weapon passed another milestone in June, when two non-nuclear designs for the weapon were flown and released successfully over Tonopah Test Range in Nevada.

The NNSA is a semiautonomous department within the Department of Energy. While the Defense Department manages the delivery systems of the nuclear force — ships, planes and missiles — NNSA has oversight over the development, maintenance and disposal of nuclear warheads.

“This result is a testament to the extraordinary dedication and skill of team members across the Nuclear Security Enterprise working together to accomplish the mission,” U.S. Air Force Brig. Gen. Ronald Allen Jr., NNSA principal assistant deputy administrator for military application, said in a statement. “It exemplifies our joint team’s steadfast commitment to fulfilling the Nation’s enduring requirements for a safe, secure, and effective nuclear deterrent.”

According to a 2016 report from the NNSA, the life-extension program will cost roughly $9.5 billion — a baseline cost of $7.605 billion, plus an additional $648 million in NNSA funding that has common applications across multiple weapon systems, as well as the estimated $1.3 billion that the Defense Department plans to spend on developing and procuring tail kits for the weapons.

However, a report by the Government Accountability Office earlier this year warned that the B61-12, among other NNSA projects, is underfunded.