The WSJ steps into the fighter wars today, with an Op-Ed discussing the effects of a load failure on an older F-15C on acquisition plans for the F-22 Raptor:

The Air Force has since discovered significant stress fractures in at least eight other aircraft, and ordered that 442 of the older-model F-15s be grounded through at least January (though 224 of the newer-model F-15Es continue to fly). Those 442 Eagles, or about a fifth of the total number of fighters fielded by the Air Force, are mainly responsible for homeland defense. They’re the ones that would have to be scrambled to intercept hijacked jetliners in the event of another 9/11.

In an alternative universe, the F-15 problem would not be significant, because the Air Force would already be flying large numbers of its designated replacement, the F-22 Raptor. But the Raptor–a fifth-generation fighter that outclasses everything else in the sky–was deemed too costly and too much of a “relic” of the Cold War. The Air Force currently has orders for no more than 183 of the planes (with some Raptor squadrons already fully operational), though there is now talk of keeping the production line open for as many as 200 more. We think it’s an investment worth making.

And a good argument to have, too. We may have for too long taken for granted the advantages that air supremacy brings to us in a brawl. There are lessons to be drawn from the fact that no US soldier or Marine has suffered an aerial attack since World War II. Those who stood against us could not make the same claim. For my own part, I would not have liked to be on the receiving end of what I have in my time dealt out. It sucked to be them.

But we need to be fiscally responsible as well. At $100 million a copy, F-22s don’t exactly grow on trees. Maybe the F-35 series won’t be “world beaters”, but we don’t expect to have to fight Eurofighters and with the Lightning II running at less than half the price of a Raptor one is reminded that “quantity has a quality all its own.” So long as a deployable force of nearly 200 F-22s is on call its hard to imagine a local adversary who could stand against up to 20 squadrons of Raptors – 10 in a two-theater fight – as well as all of those USAF, USN and USMC F-35s. For the sake of clarity, I leave out for now our coalition allies.

The real question planners and budgeteers ought to be asking is not whether an obsolescent and potentially decrepit F-15 force can defend the mainland US from aerial attack. As an island nation, we are still fortunate in that continental air defense is a 1% mission at best and in any case another 100 Raptors wouldn’t appreciable improve kill ratios against hijacked airliners. Furthermore, for “away games,” if the F-15C is not capable of standing up to Su-35s, then it doesn’t much matter how many cracks there are in the load-bearing members. We don’t send our guys out to die in inferior gear – it’s terrible for morale.

The homeland defense mission could be absorbed by Air Guard F-16s or augmented by shore based Navy and Marine Corps FA-18s in times of increased tension. That’s not much fun nor is it very good training for the Leviathan forces, but the fact of the matter is that they stood up after 9/11 when all the airliners were grounded and the weekend warriors couldn’t travel from their airline domiciles to their Air National Guard bases.

Nor is this an either/or question of simply buying what you can and hoping for the best. The USAF should be (and undoubtedly is) looking at the threat, defining a capability suitable to overcoming that threat and illuminating whatever risk is inherent in a capability shortfall.

It’s always correct to say “more is better,” because, frankly, it is. What’s harder is to ask is “how much is enough?” That’s the question that needs answering. When you’ve modeled that out, add 10%, in case you worked the math wrong. And then add another 10% because, in the end game?

Congress, knowing that you’ve padded your numbers 10%, will screw you every time.