On 11 December, the Boeing F-15E Strike Eagle marked the 26th anniversary of its first flight, but the venerable strike fighter will continue serving with the US Air Force well into the 2030s.

“There are no plans to replace the F-15E for the foreseeable future,” the USAF says/…/

It is not surprising that the USAF does not have a plan in place to replace the F-15E, says Mark Gunzinger, an analyst at the Center for Strategic and Budgetary Assessments. “They have a lot of things to address right now, for example, funding in this pretty ugly budget environment for their three top priorities, which remain the [Lockheed Martin] F-35, [Boeing KC-46] tanker, and the [Long Range Strike] bomber.”

The most obvious candidate to replace the F-15E is a variant of the F-35, Gunzinger says. There is no money to develop a clean sheet design. “I do think they’ll do some kind of an F-35E or whatever kind of F-35 variant,” he says.

Indeed, industry officials say that there have been detailed studies done to build a two-seat F-35 along with extended-range models. Both are “doable,” and are not mere theoretical constructs. Particularly, if the USAF Research Laboratory’s adaptive engine technology development (AETD) programme yields an operational engine, it could help extend the F-35′s range. That is if the AETD lives up to its promises of delivering better than 35% fuel efficiency compared to the existing Pratt & Whitney F135. Pratt & Whitney and General Electric are working on competing designs for the AETD programme.

Gunzinger says that he does not doubt that building a two-seat F-35 is possible, but he questions if there is a need to do so. What would be more important, he says, is extended range and increased payload. Adding a second seat would require a more extensive redesign, which on a stealth aircraft is even more challenging than on a conventional jet, Gunzinger says. In any case, building a larger version of any stealth aircraft is practically as challenging as designing an all new aircraft. “Could you do it? Yeah, but it’s probably more expensive than sticking with a single seat.”