Sen. John McCain, chairman of the Senate Armed Services Committee, lit into Air Force leadership on Thursday, saying the service was ignoring the facts about the effectiveness of the A-10 "Warthog."

McCain slammed Gen. Mark Welsh, the Air Force Chief of Staff, saying the general was being "disingenuous" and that his answers were "embarrassing."

The exchange became heated, with McCain repeatedly interrupting Welsh before finally cutting the conversation off by saying "Enough general, OK?"

Welsh said he wishes the service could keep the A-10, but that the limited funding, resources, and maintainers available means the Air Force will need to shift personnel from the Thunderbolt II to the new F-35 Lightning II.

"We have X amount of people and X amount of dollars," he said.

"And you have X amount of missions and the A-10 is carrying out those missions, general," McCain cut in.

The close-air support (CAS) role of the A-10 would be taken over by the F-15E Strike Eagle until the F-35 starts deploying after it reaches initial operating capability near the end of this year, Welsh said.

But that answer didn't satisfy McCain, who questioned why the Air Force wasn't using the F-15 for CAS now.

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"You have nothing to replace it with, general," the Arizona Republican said. "You have nothing to replace it with. Otherwise you'd be using the F-15s and the F-16s which you have plenty of. But you're using the A-10 because it's the most effective weapon system."

The Air Force's argument "flies in the face of reality," McCain told Welsh.

"You know general, I've had a little military experience myself including in close-air support, and for you to sit there and tell me that we could be using the F-16 and the F-15 when we're not, and your plans are to use the F-35 at ten times the cost, eventually it flies in the face of not just my experience but the experienced pilots that I know, the U.S. Air Force pilots that I'm in constant communication with."

The Air Force and Congress have long butted heads over the A-10 retirement. The Pentagon has tried several times to retire the aircraft, each time to be overruled by Congress, lawmakers even going so far as to put language in the budget that would prevent the decommissioning of the plane.

In the budget proposal for fiscal 2017, the Air Force finally relented, and said it would keep the plane on board until 2022, though there are plans to retire large numbers of the aircraft in 2018 and 2019. Yet McCain's comments showed that the Air Force is once again unlikely to find allies in Congress for its plans.

"It's really embarrassing to hear you say something like that when I talk to the people who are doing the flying, who are doing the combat who say that the A-10 is by far the best close-air support system we have. It's embarrassing," McCain said.

"We all talk to them," Welsh replied.

McCain was joined by other members of the committee in expressing their concern, including the top Democrat, Sen. Jack Reed.

Reed said it was "not clear that the close-air support capability of the future force will equal or exceed that of the current force."

Welsh said he is in a difficult position, and being forced to argue for retiring the A-10 despite not wanting to do it. Yet the lack of funding and stress on airmen is forcing his hand, and the Air Force must shift resources over to newer fifth-generation planes, he told the committee.

McCain also criticized the budget proposal for the Air Force, saying that it places "an unnecessary and dangerous burden on the backs of our airmen."

"The President should have requested a defense budget that reflects the scale and scope of the national security threats we face and the growing demands they impose on our airmen," McCain said. "Instead, he chose to request the lowest level of defense spending authorized by last year's budget agreement and submit a defense budget that is actually less in real dollars than last year."

Despite criticizing the F-35's ability to replace the A-10, McCain said the service still needs the fifth-generation stealth fighter, and argued that delaying the purchase of the fighter would exacerbate the service's modernization woes.

"The service's latest procurement profile now projects the last F-35A to be delivered in the year 2040," McCain said. "At a certain point, a 38-year acquisition program runs the risk of producing obsolescence, especially when our adversaries are accelerating technological developments to counter the F-35."

McCain also slammed the high cost of the fighter, estimated to be $100 million per plane. With delays, the cost per plane is likely to go up, and the Air Force won't get the foreign sales it expects to offset some of that expense, the senator said.

The senator pointed to the election of new Canadian Prime Minister Justin Trudeau, who said his country won't purchase any F-35s. McCain said that both Welsh and Secretary of the Air Force Deborah Lee James seemed to be ignoring that information when arguing about program costs.