WASHINGTON — The Air Force general who oversees long-term strategy downplayed the potential retirement of its F-15C/D Eagle fleet — an idea the service is considering but has not yet approved.

"We intend to maintain the F-15C fleet through the 2020s," Lt. Gen. Jerry Harris, deputy chief of staff for strategic plans, programs and requirements, told reporters after a congressional panel.

The proposed F-15C/D retirement first became public after Rep. Joe Wilson, R-S.C., asked Lt. Gen. Scott Rice, director of the Air National Guard, about it during a hearing last week. Rice confirmed that the service was indeed considering replacing its F-15Cs and Ds with F-16s, although the Air Force would retain its inventory of F-15E Strike Eagles.

At the current time, Harris said the Air Force does not plan on retiring the first F-15C or D until at least 2020, although officials noted that its retirement has not been written in stone and could change on a year-to-year basis.

Harris pointed to two factors that could drive the F-15's exit: an increasingly high-end threat environment — where fourth-generation platforms like the Eagle may not prove as effective — and the age of the aircraft. which is nearing the end of its service life.

"Most of these [F-15C/Ds] were designed in the late '60s and '70s and are not appropriate for the threat that we have," he said. "I would expect that most airplanes that have service life we would continue to fly until they're done with that. The F-15C/D fleet times out in the mid 2020s. The F-16s, we have additional service life that is available, same with our F-15E fleet and some of our A-10s."

The decision could also be partially driven by how quickly the Air Force can acquire the F-35, Harris added. The service has made increasing its buy rate to 60 F-35As a year a priority, and may be loath to retire the F-15C/D unless it has a sufficient number of joint strike fighters.

The Air Force has about 230 F-15C/Ds, and all are owned by the Guard except for a couple squadrons at Kadena Air Base in Japan, and RAF Lakenheath in England, which are paid for by special funding designated for training and exercises with European allies. Should the service decide to retire the C and D models, it could give the Guard F-16s to accomplish the homeland defense mission.

"We will use fourth-generation at home, we will use them abroad where we can, but when it comes to fighting in some of these congested air spaces, fourth-gen does not have much of a role five, 10 years from now, even with upgrades to them," Harris said.

Sen. Elizabeth Warren, the Massachusetts Democrat who raised the topic of the F-15’s retirement, told Air Force officials that she hoped any future decision would include input from the Air National Guard. She also questioned whether getting rid of the aircraft would be a good choice, given the service's readiness problem.

"Given its cost, I realize that we may not be able to procure the F-35 in the numbers the Air Force has planned until 2045, and I'm also not convinced the F-16 is fully capable of replacing the F-15 in meeting the air-to-air mission," she said. "I just want to raise the point, because it seems to me that retiring hundreds of aircraft at a time when the Air Force is in need of additional capability may not make a lot of sense here."

Correction: The original version of this story misidentified the number of bases with F-15C/D aircraft assigned to the active duty Air Force. Both RAF Lakenheath and Kadena Air Base currently host F-15C/D squadrons.