By Aaron Gregg / The Washington Post

A high-stakes competition to rebuild a critical component of America’s aging nuclear arsenal was narrowed down to two companies Monday, as the Air Force awarded Boeing and Northrop Grumman the next phase of a contract to replace the Minuteman ground-based inter-continental ballistic missile.

In a contract award announced by the Air Force on Monday afternoon, the two companies were awarded $349.2 million and $328.6 million contracts respectively for improving upon the key strategic deterrent. The decision effectively rejected a bid by Bethesda, Maryland-based Lockheed Martin.

Boeing and Northrop now have three years to develop the next ground-based strategic deterrent missile, after which a single company is to be selected to run the program.

“The Minuteman III is the enduring ground-based leg of our nuclear triad. However, it is an aging platform and requires major investments to maintain its reliability and effectiveness,” Air Force Gen. Robin Rand, commander of Air Force Global Strike Command, said in a statement. Producing an advanced ground-based missile “is the most cost-effective ICBM replacement strategy, leveraging existing infrastructure while also implementing mature, modern technologies and more efficient operations, maintenance and security concepts.”

Inter-continental ballistic missiles produced and maintained by Boeing under the Minuteman program have been at the center of the U.S. military arsenal since the late 1950s. The weapons make up one leg of the United States’ so-called nuclear triad, which includes the capability to launch nuclear missiles on a moment’s notice from air, ground and submarine.

“As the Air Force prepares to replace the Minuteman III, we will once again answer the call by drawing on the best of Boeing to deliver the capability, flexibility and affordability the mission requires,” Frank McCall, Boeing’s program manager for the effort, said in a statement.

The Pentagon has been working to overhaul all three legs. The Navy’s Columbia-class nuclear submarine is slated to replace Ohio-class submarines sometime after 2020. And a contract decision on the long-range stand-off missile, meant to launched from a B-52 bomber, is slated for later this week.

For the ground-based version awarded Monday, whichever company comes out on top will be the recipient of a windfall of defense spending. Costs of the program have been estimated to be at least $85 billion.

The Defense Department’s decision Monday comes as a blow to Lockheed Martin, which is still smarting from a major loss on the B-21 stealth bomber. The firm had put together a star-studded list of subcontractors that included defense manufacturer General Dynamics to build the missile’s various control systems, Bechtel to control its launch systems, and Orbital ATK and Aerojet Rocketdyne to jointly handle propulsion. Boeing and Northrop have declined to name their partners on the contract bid.