The U.S. military’s F-35 stealth fighter has finally flown in combat for the first time.

But after 17 years of development costing nearly $60 billion, the controversial jet still has a lot to prove.

At least one of the radar-evading F-35s conducted an air strike in support of what the U.S. Navy described as "ground clearance operations" in Afghanistan on Thursday morning, local time. U.S. military fighters usually fly in formations of at least two planes.

"The strike was deemed successful by the ground force commander," the Navy stated.

The Israeli air force in May announced that its own F-35s had flown air strikes along "two different fronts in the Middle East." Israel regularly bombs militants and regime targets in Lebanon and Syria.

Unlike the Syrian regime, insurgents and terrorists in Afghanistan do not possess the radars and surface-to-air missiles that Lockheed Martin designed the F-35 to defeat. While Israel apparently sent its F-35s into harm's way, the American jets made their combat debut in a relatively benign environment.

“From the incomplete reports I’ve seen, they flew a mission other aircraft have flown thousands of times at a fraction of the cost,” Dan Grazier, an analyst with the Washington, D.C.-based Project on Government Oversight, told The Daily Beast. “This is obviously a moment the program’s boosters have been looking forward to for some time.”

But that's not to say the military deliberately staged the air strike in order to safely give the F-35 its first chance to fight in an American war. "I doubt whether it was seriously done just to use the F-35, but rather that happened to be the squadron in theater," Brian Laslie, an air-power historian and author of The Air Force Way of War, told The Daily Beast.

The Marine Corps formally declared its first F-35 squadron ready for war back in 2015. The Air Force did the same with its own lead F-35 unit in 2016. "It’s operational," Laslie said of the stealth fighter. "They’re going to use it."

With its angular, radar-scattering shape and special, radar-absorbing surface coating, the F-35 in theory can avoid detection by some kinds of enemy air defenses, putting it roughly in the same class as the Air Force's older F-22 stealth fighter and B-2 stealth bomber.

But throughout its lengthy development, the F-35 has been dogged by design flaws, mechanical failures, delays and cost overruns, caused in part by the need to design three separate models of the plane to suit the U.S. Air Force, Navy and Marine Corps.

The F-35s that struck targets in Afghanistan on Thursday were vertical-landing F-35B models belonging to Arizona-based Marine Fighter Attack Squadron 211. The F-35s launched from the Navy assault ship USS Essex sailing on the Indian Ocean.

“The F-35B is a significant enhancement in theater amphibious and air warfighting capability, operational flexibility and tactical supremacy,” Vice Adm. Scott Stearney, commander of U.S. naval forces in the Middle East and Central Asia, said in a statement.

Leaving aside development costs, an F-35 sets back taxpayers between $90 million and $120 million apiece, depending on the model. The price is dropping as Lockheed produces more and more of the jets. Congress authorized the Pentagon to buy 93 new F-35s in 2019, adding to more than 200 of the planes that are already in U.S. service and scores more that are in production.

But Lockheed and the military have struggled to maintain the complex jets. In October, the Government Accountability Office found that the military is six years behind schedule in developing repair facilities for the F-35. The delay "has resulted in average part-repair times of 172 days—twice the program's objective," the GAO reported.

The maintenance backlog threatens military efforts to expand the F-35 fleet. The Air Force, Navy and Marines combined say they need 1,763 F-35s to replace older planes including A-10 attack jets and F-15, F-16 and F/A-18 fighters.

Critics say the F-35 is in some ways is actually inferior to the older jets. In July the Air Force pitted the F-35 and the A-10 against each other in simulated combat. The trial, mandated by Congress, was supposed to establish whether the delicate, lightly armed F-35 could effectively replace the rugged, heavy-lifting A-10 on the most dangerous missions supporting ground troops under fire.

The Air Force designed the secretive test to favor the F-35, Grazier wrote. "Our troops deserve better than a surreptitious test rigged in favor of a weapon that can’t do the job and against the one that can.”

Undeterred by controversy, this month the Air Force announced a plan to add, by 2030, 74 new squadrons to its existing 312 squadrons—all in order to match Russia and China's own military build-ups. "The Air Force is too small for what the nation is asking us to do," Air Force Secretary Heather Wilson stated.

The expansion, which is contingent on congressional approval and tens of billions of dollars in extra funding, would include seven new fighter squadrons on top of today's 55 fighter squadrons. If the Air Force wants to equip those new squadrons with F-35s, it could need as many as 200 more of the stealthy jets.

But even if Congress agreed to pay for the new planes, it's not clear that the Air Force could maintain them. Moreover, the flying branch would need to recruit and train hundreds of additional pilots at a time when it's already short 2,000 of the roughly 20,000 pilots it needs to crew all of its current fighters, transport planes and helicopters.

Service leaders blame the pilot shortfall on the airline industry's growing demand for flight crews. In 2017, Air Force lieutenant general Gina Grosso told the House Armed Services Committee that strong airline hiring could continue "for the next 10 to 15 years," threatening military efforts to hire all the pilots it needs.

Vexed by maintenance and aircrew shortfalls and struggling to prove itself against the older planes it's replacing, the F-35 is still very much a work in progress. But it's a work in progress that finally has dropped live bombs in combat.

That's something. Even if the enemy it targeted in its first strike had no way to shoot back.