IN THE 1990s, the Pentagon solved its budget problems in part by taking what some now call a procurement holiday. Because it was reducing force sizes, it had excess equipment -- planes, tanks, ships, etc. -- and felt able to cut back on buying new ones. One result is that "stocks of many kinds of military equipment" have been allowed to reach "a higher average age than . . . in the past," the Congressional Budget Office recently reported; more equipment than usual is closer to the likely end of its useful life.

To reverse the trend, as sooner or later it must, the Pentagon will have to increase procurement spending by billions more than current long-range budget estimates allow, CBO has warned. To go beyond simple replacement and buy more sophisticated equipment will require even greater sums. The underfunding is a problem that, up to now, the politicians have tended to blink. Who wouldn't rather talk about tax cuts or aid to the elderly or other domestic needs than possible unmet military needs in time of relative peace? But the mismatches in the military budget aren't going to go away. Last month's unexpected vote by the House in favor of a "pause" in procurement of the costly F-22 fighter plane could be a healthy sign that a serious subject is about to get its due.

In no part of the military budget is the gap between projected need and likely resources greater than with regard to tactical aircraft -- fighter planes. The military has three new fighters on the drawing board. Its current plan is to buy a total of 3,700 over the next 27 years to replace the six kinds now in use. CBO estimates the cost at $340 billion in today's dollars. That would represent a huge increase in current rates of spending (and is not the only area in which procurement costs could be expected to rise). The defense budget would have to go up much more than currently envisioned, or other categories of defense spending would have to come down (unlikely) -- or a decision could be made to make do with less, or less costly, tactical air capability. If the House vote forces a serious public weighing of these alternatives, it will have done a great service.

The F-22 is envisioned as a top-of-the-line fighter that would guarantee U.S. forces continued control of the air, and all of the overwhelming advantages that such control implies and the country has come to expect, in future conflicts. The problem is that the plane has proven extremely costly. It has left the original estimates as far behind as its backers say it would leave future adversaries. At the current estimate of $200 million a copy, more or less, it would be more than twice as expensive as the highly effective F-15 it would replace. Among the questions to be answered is whether, in the end, it will really be that much better than the F-15, or the larger number of upgraded F-15s that likely could be had for the same price. Not all the systems on which the effectiveness of the F-22 would depend have yet been tested. Can it be made to work?

Even if the answer is yes, critics raise the further question of whether it is worth it. Given other demands on the dollar, how much sense does it make to spend heavily to provide the Air Force with that great an increase in capability when no other air force in the world is close? Defenders respond, in part, by noting that other air forces can be expected to improve, and that more than $20 billion has already been spent on development of the F-22. It can't be recovered. The real debate is about the incremental amount that either will or won't be spent, which the Pentagon says would be less than $100 million a plane but CBO puts at $125 million. Those reluctant to choose between the cost of buying the plane and the risk of doing without it suggest, as a possible compromise, buying fewer than the 339 the Air Force contemplates (itself a reduction from the 750 envisioned originally). Some would also put part of the squeeze on the other new fighters the services want to buy.

In the end, these are political decisions -- the balancing of likely costs and risks. The affected members can be expected to make them on the basis of where the jobs are as well -- whose states or districts are likely to win or lose. That's part of the process. The important thing is to have a more serious public debate than has thus far occurred. Our sense is that CBO is right in warning as it has for years that current budgets aren't enough to cover all the defense costs they are supposed to. If the budgets don't go up, some of the things they are supposed to buy will have to be forgone. The tactical air debate is part of a broader discussion, and as good a place as any to start.