The largest buyer of the F-35 just declared it ready for war

The largest buyer of America's most expensive weapons program just declared it ready for war.

Of the sister service branches, the US Air Force has been the most bullish on Lockheed Martin's F-35 Lightning II's combat capabilities.

The 12 Air Force F-35A jets, and the 21 combat-mission-ready pilots from Hill Air Force Base's 34th Fighter Squadron, represent a significant breakthrough for the weapons program which began development 15 years ago and has been offset by design flaws, cost overruns, and technical challenges.

As the Air Force is buying nearly 70% of the fifth-generation jets being made domestically (1,763 of 2,443 aircraft), the Air Force sets the economies of scale for the tri-service fighter, with each plane costing a cool $100 million.

Lockheed Martin, considered a bellwether for the US defense sector, is expected to generate nearly a fifth of its $50 billion in 2016 sales solely from the F-35 program.

In the company's latest quarter, the defense giant posted net sales in its aeronautics business up 6% or $244 million (compared to same period in 2015).

The Pentagon's top weapons supplier is also building the "jack of all trades" aircraft for the United Kingdom, Turkey, Australia, Italy, Denmark, Norway, Netherlands, Israel, Japan and South Korea.

Even though the Air Force is currently operating the oldest fleet in its history, it's the last of the sister service branches to declare its variant combat ready.

Last summer, the Marine Corps was the first of the military branches to declare initial operational capability (IOC) for 10 F-35B jets.

"There were a lot of people out here in the press that said, 'Hey, the Marines are just going to declare IOC because it would be politically untenable not to do that," Lt. Gen. Jon Davis, deputy commandant of the Marine Corps for aviation Davis said during a discussion at the American Enterprise Institute on the readiness and future trajectory of Marine aviation.

"IOC in the Marine Corps means we will deploy that airplane in combat. That's not a decision I was gonna take lightly, nor Gen. Dunford," Davis said.