ORLANDO, Fla. – The Air Force’s two senior leaders made clear Feb. 28 that the decision to procure a new variant of Boeing’s

[BA] F-15 fighter jet is tied to increasing aircraft quantities, while continuing to buy more F-35 Joint Strike Fighters within the budget constraints the service has today.

The Air Force’s initial fiscal year 2020 budget proposal “did not include additional fourth-generation aircraft,” Secretary Heather Wilson said at a Thursday media roundtable at the Air Force Association’s Air Warfare Symposium here, confirming reports that new F-15X platforms were not originally in the service’s plans.

Boeing’s F-15 Advanced Eagle, an upgraded version of the F-15E Strike Eagle. (Photo: Boeing)

But the final FY ’20 budget proposal is a culmination of input from the services and the broader Pentagon, she noted. “It is not something that is just an Air Force decision. Ultimately, it’s a Defense Department budget and that rolls into an overall presidential budget.”

The Air Force is expected to include a number of F-15X aircraft – an upgraded version of the F-15E Strike Eagle – in its forthcoming budget proposal, currently slated to be released mid-March. Bloomberg recently reported that the service will ask for eight aircraft in the FY ’20 budget, but could ultimately buy up to 80.

Air Force Chief of Staff Gen. David Goldfein said that capacity was needed to “execute the national defense strategy to a level of moderate risk.”

But he emphasized that the Air Force is “first and foremost adamant about the keeping the program of record of the F-35 on track” to eventually procure 763 aircraft. That being said, “the money was not available” to procure more F-35 aircraft than they already have included in the FY ’20 budget request, and Wilson attributed that deficit to sustainment costs over time rather than initial procurement costs.

“When you look at average lifespan of the aircraft … fourth-generation fighters are less expensive to sustain than fifth-generation fighters are,” she said. “That was a factor in the money we had available.”

Asked point blank during the media roundtable whether the Air Force wanted to buy F-15X aircraft, Goldfein replied, “We want new airplanes.” Specifically, the service wants to buy 72 aircraft per year, up from about 48 now, Wilson added.

Air Combat Command Commander Gen. James “Mike” Holmes echoed that sentiment in a subsequent media roundtable, saying “72 is a good target” for the Air Force to keep their fleets in operation while maintaining aircraft at a sustainable rate.

“If the balance is, we’re going to have a mix of fifth- and fourth-gen and that’s how we afford getting to 72 a year, I think that’s great,” he said. “No matter what we do, or however many we buy, we’re going to have a fourth- and fifth-gen mix for years to come.”