Is that the reason? I thought it was the need to counter the Chinese strategy of mass producing fighters with an idea of overwhelming western fighters through sheer weight of number. F35 is weak on per hour running cost and uptime per unit, and loses to the F15 variant if you are looking to scale.
The f35 can operate in a similar role to an e8 alongside a mix of cheaper aircraft.
> F-15EX in particular can carry patently ridiculous payloads.
But also this. Which touches on F35 being very complicated to develop for, and taking ages to integrate weapons vs F15s. And some operational considerations like not wanting to retrain F15 pilots.
Look at USAF 4+1 for next 15 years of procurement. Basically F35A, F15EX, F16CD, A10s and +1 being F22s that will be replaced by NGAD.
Read between the line consideration is F35/F22 was made for Europe/RU theatre, lacks range in PRC theatre without tanking, which are vunerable to J20s with longer range and air to air. Hence NGAD being mid sized bomber, and acquiring 100 B21s that cost as much as 1000 F35s.
>Adding new F-15s was not an Air Force idea, but instead came out of the Pentagon’s Cost and Program Evaluation office, or CAPE, and was endorsed by former Defense Secretary James Mattis. While the Air Force’s long-held position has been to invest only in fifth generation fighter technology, it has defended the plan to buy new F-15s as a way to maintain fighter capacity, given the aging of the F-15C fleet and the slow pace of F-35 acquisitions.
>While the Air Force is adamant that buying F-15EXs will not reduce the requirement to build 1,763 F-35s, history and the Air Force’s own budget request suggests otherwise. The 2020 budget submission shows the Air Force buying 24 fewer F-35s over the next five years compared to last year’s plan.
Further reading: https://www.airandspaceforces.com/article/f-15ex-vs-f-35a/