Fifth-generation fighters may be the air frames of the future, but that future may not be quite as close as it seems. When it comes to the dog fights of the 21st Century, America may now be looking toward a workhorse of the past under the guise of the new F-15X program.

The F-35, often touted as the most advanced fighter platform on the planet, may one day serve as the general purpose workhorse of American military aviation, but to date, there remains too few functional F-35s to serve as the nation’s aerial backbone. Likewise with the already canceled F-22 Raptor program, which boasts only around 150 operational fighters and the expectation that those numbers will continue to dwindle as the years ware on.

Even if the F-35 production could be ramped up, it still wouldn’t fill a vital gap that’s beginning to develop in America’s national defense apparatus: the need for a high-speed, air intercept fighter. For all its strengths, the F-35 was never designed to serve as a dedicated dog fighter, particularly because the prevailing idea among politicians at the time was that the days of aerial combat among near-peers were over forever.

Two decades of combat operations against insurgent and terrorist groups relieved the U.S. military of the need for speed or acrobatics in flight, leading to the happy dismissal of the much faster F-14 Tomcat in favor of the Super Hornet in the Navy, and allowing the Air Force to set aside its F-22 program in favor of the slower F-35.

Both the Super Hornet and the Joint Strike Fighter would fare better than the (incredibly expensive to maintain) Tomcat or Raptor in most missions tasked to a “multi-role” fighter, but with an increased emphasis on the possibility of a future war with China, America needs fighters that can go toe to toe with the likes of a non-stealthy but highly acrobatic Su-35 or the as-yet untested — but F-22 based — J-20. America also needs fighters that were built to be fighters in order to round out its air presence. Despite being 32 years old, the F-15s in service remain the fastest fighters in Uncle Sam’s arsenal.

That’s where Boeing’s F-15X concept comes in. Boeing has been aggressively pursuing ways to keep their various air frames in the fight for years to come, including accepted pitches for Block III upgrades to the Navy’s fleet of Super Hornets, as well as notably more mad scientist-esque endeavors like adding wings and pusher-propeller to the Apache and turning the B-1B Lancer into a supersonic gunship. It would seem that the Pentagon, particularly Patrick Shanahan, who has been serving as Deputy Defense Secretary under Mattis since last July and is now slated to take over as acting Secretary on January 1, sees the F-15X program as a feasible endeavor worth exploring. The rumors are that the push for the F-15X comes from the Pentagon, rather than within the ranks of the Air Force itself.

It’s worth noting that Shanahan previously served as an executive within Boeing and has recused himself of all decisions pertaining to Boeing programs — though it’s unclear as to how that will play out with him heading the Defense Department.

The F-15X would not be a new air frame, but rather a freshly built F-15 that incorporates decades worth of technological advancements over the fleet of F-15C/Ds the Air Force currently maintains. Many of these advancements have already made their way onto F-15s being sold to allied Air Forces in Saudi Arabia and Qatar, under the titles F-15SA and F-15QA. This makes it a particularly appetizing possibility for the Defense Department, which is currently faced with either an expensive update effort to keep their existing F-15s in the air (three decades after they first entered service) or a controversial initiative to equip F-16s with active Electronically Scanned Array (AESA) radars and have them replace the F-15 as it flies off into the sunset.

Either initiative would be costly, and both would really only serve as a means to delay the aging aircraft problem by a few more years. Boeing’s proposal would include new F-15s that would require far less work to maintain, resulting in a significant cost reduction and potentially paying for the cost of purchase in savings within the first decade or so. Boeing claims the F-15X would boast superior capabilities over the previous F-15s for a reduced hourly operating cost and, they claim they’ll fly for 20,000 hours before the Air Force would need to revisit concerns about an aging fighter fleet.

Currently, the Air Force is expected to include $1.2 billion in its 2020 budget request to procure 12 new F-15Xs, though the announcement won’t be made official until February and much can change by then.