Even among fans of Boeing’s F-15EX initiative, you won’t find anyone who will contend that the F-15 is a superior aircraft to Lockheed Martin’s Joint Strike Fighter. On paper, a new F-15 does offer a number of advantages over the stealth F-35—higher top speed, lower operating costs, larger payload capacity, and greater operational range—but in a fight, the F-35’s low observability and data fusion capabilities make it an apples and oranges comparison. The F-35 is, in many ways, the future of American air power. Purchasing new F-15s then, one could contend, is a step backward.

So if there’s no real debate regarding which is the better fighter, why would the Air Force allocate more than a billion dollars to the purchase of a new batch of F-15s in 2020? The explanations the American people have gotten from the U.S. Department of Defense (DOD) have varied over the past few months, and often seem less than satisfying.

“One of the considerations was the diversity of the industrial base,” a defense official told journalists at the Pentagon last Friday. “Maintaining a diverse industrial base is in the best interest of the Department of Defense. The more diversity, the more competition…and the better prices we have.”

It’s easy to see why that justification for a multi-billion dollar defense initiative doesn’t quite sit right with many. The DOD is in the business of winning wars, not providing corporate handouts to keep contractors in business during the era of the F-35. If the Pentagon believes the F-35 is the better aircraft for the conflicts America may soon find itself in, why isn’t it throwing that $1.1 billion allocated for the F-15EX in 2020 at securing another 10 F-35s instead?

The DOD’s explanations for the F-15EX purchase have also included more robust and logical responses such as concerns about keeping existing F-15 airframes flying for as long as we need them and F-35 production limitations that could result in America not having enough aircraft to fulfill its combat obligations in the years to come. The problem is there’s another element at play here that tends to go undiscussed in defense media: America is in the business of selling F-35s to its allies, so the Pentagon needs to be particularly careful about how it discusses them in the press.

Acting Defense Secretary Patrick Shanahan is currently under investigation following allegations that he has benefited his previous employers at Boeing in his new role, often expressing frustration with the F-35 program and claiming that Boeing would not have had similar issues. Inappropriate as those remarks may be coming from a senior defense official, a number of recent reports seem to substantiate some of Shanahan’s frustrations.

The Navy variant of the F-35 was recently declared combat operational despite averaging an anemic five percent readiness rate throughout the last year. The F-35A (Air Force iteration) continues to struggle with issues related to its close air support gun. Test airframes of the F-35B (vertical landing variant) have begun to show stress fractures in the airframe, suggesting that some of these jets will have a far shorter lifespan than originally anticipated. These issues (and a laundry list of others) are not insurmountable by any stretch of the imagination, but they do show that the F-35 program still has some kinks to work out before these planes are able to serve as America’s primary air platform.

These issues, rather than the F-15EX purchase, are likely why F-35 purchases were slightly scaled back compared to projections for 2020. However, the Pentagon needs to be careful in how it goes about doing these things, as these aircraft are not just going to serve in America’s armed forces, sales are already pending in more than a dozen other countries. Making public statements about the F-35 program setbacks could have a huge effect on those sales efforts and on Lockheed Martin, the government’s largest and most diverse weapons supplier. Any official discussion of purchasing new F-15s needs to carefully avoid any statement that could portray the F-35 or Lockheed Martin in a negative light. Those careful considerations can often leave the explanations feeling abbreviated or incomplete as a result.

So why is the Air Force getting new F-15s? The truth is there are a number of overlapping reasons ranging from F-35 operating cost concerns to wanting to ensure America has a variety of platforms available for different types of combat operations. These questions don’t lend themselves to simple answers because no multi-billion dollar decision ever includes simple variables. The F-35 may still prove to be every bit as good as promised, but it seems there’s still some work to be done before it reaches that point.