WASHINGTON — Three squadrons of A-10 Warthogs will go out of service unless the Air Force comes up with funding to pay for new wings, the head of Air Combat Command confirmed in an exclusive interview with Defense News.

Although the Air Force fully funds the operations and maintenance of all nine A-10 squadrons in its fiscal 2018 budget request, Lt. Gen. Arnold Bunch, the service's top uniformed acquisition official, and Lt. Gen. Jerry Harris, its deputy chief of staff for plans, programs and requirements, committed in written testimony to Congress to retaining only six squadrons long term.

The crux of the issue, according to head of Air Combat Command Gen. Mike Holmes, is that new wing sets have been ordered for only 173 of 283 Warthogs, or about six squadron's worth.

Exactly when the Air Force will drop down to six A-10 squadrons will depend on multiple factors, including operational tempo over the next few years and the buy rate of the F-35. But Holmes said the first planes could be phased out within five years, as their wings run out of service life.

"When their current wings expire, we have some flexibility in the depot, we have some old wings that can be repaired or rejuvenated to go on. We can work through that, so there's some flex in there," he said in a June 8 interview. "We're working on a long-term beddown plan for how we can replace older airplanes as the F-35 comes on, and we'll work through to figure out how we're going to address those A-10s that will run out of service life on their wings."

The Air Force "can continue to provide close air support across the spectrum of conflict with those 173 airplanes," he added.

Although an A-10 follow-on aircraft — sometimes called A-X — is still on the table, Holmes noted that decision would come further in the future as the Air Force contemplates whether to replace the remaining 173 A-10s with a purpose-built close air support platform in the late 2020s.

Confirmation of a move to eliminate even a portion of the A-10 fleet will likely inflame ardent supporters of the aircraft in Congress, who have in prior years prevented the service from retiring the aircraft.

Holmes noted that the Air Force’s current plan to mothball three A-10 squadrons adheres to the 2017 defense authorization bill, which mandates that the service maintain 171 A-10s until the Pentagon’s director of operational test and evaluation conducts comparative tests between it and the F-35. However, he acknowledged that "Congress gets the final say on everything we do" and could try to prevent any divestitures.

During a House Armed Services Committee hearing Wednesday, Rep. Martha McSally, R-Ariz., asked Bunch and Harris to explain the Air Force’s apparent decision to cut a third of its A-10 squadrons. McSally, an A-10 pilot herself, represents Davis–Monthan Air Force Base, which is home to three A-10 squadrons, according to Air Force data.

"From my view and my experience, if we need that capability until a proven, tested replacement comes along, nine squadrons is the absolute minimum," she said. Due to House votes, the hearing was called to a close before McSally could receive an answer from Bunch and Harris.

The most obvious move Congress could make would be to fund the $103 million for A-10 wings included in the service’s unfunded priorities list, but that only covers a portion of the remaining 110 aircraft in need of rewinging.

"That would buy us time. Their wings don’t all run out of service life at the same time, it depends on the individual airplane," Holmes said. "We have the money in the unfunded list to get another contract for wings and to get a batch that would help us work through a period and give us time to buy more wings for the rest of the fleet if we are unable to go forward to drop down to six squadrons."

Boeing is under contract to provide the 173 wing sets, with an option for 69 more. The company has estimated that new wings would allow A-10s to remain in service into the 2030s.

At this point, the Air Force has not identified which A-10 squadrons would be phased out or which aircraft would replace the Warthog at selected installations, Holmes said. One option is to replace Warthogs with F-35s, but because the A-10 can operate on a shorter runway, not all bases would be able to host the Joint Strike Fighter. In that case, perhaps A-10 squadrons could adopt fourth generation fighters from squadrons moving to the F-35.

"I don’t think we’ve made a decision on any of that just yet," he said. "I believe that will be a part of the ’19 budget process, and because most of that happens outside of the five year defense plan that we turn in, we still have options."