In a letter to new Defense Secretary Leon Panetta last week, Senators Carl Levin and John McCain, the top men on the Senate Armed Services Committee, suggested it was time to look into terminating the F-35 Joint Strike Fighter program. Angered by cost increases for the first three lots of low-rate production on the Lightning, the two senators asked Panetta to tell them "what would be our legal obligations and our costs if we were to terminate the F-35 program now."

No doubt the legal and monetary obligations would be great, but the strategic, operational, and defense industrial consequences of terminating the F-35 program would be catastrophic. To begin with, the F-35 is a multinational program. To kill it would not only yank the rug out from under America's closest friends and allies- long-time partners like Great Britain, Australia, and Canada, for example- but destroy the prospects for closer partnerships in the Middle East and, particularly, the Asia-Pacific, where Japan, Korea and Singapore are likely F-35 customers. And it would forestall the opportunity to share a common fifth-generation aircraft with others like India, which could only turn to Russia or try to develop such an aircraft on its own. Terminating the F-35 would be the clearest signal one can imagine, even beyond retreat from Iraq or Afghanistan, that the United States no longer will assume the burdens of international security.

"And with few other procurement programs left- across any of the military services- the F-35 is a big, juicy target for people wearing green eyeshades."--Thomas Donnelly

Terminating the F-35, or simply terminating the F-35B short take off vertical landing (or STOVL), would be fatal for the Marine Corps as a serious war fighting service. The modernization of the Marines is already at risk; the V-22 Osprey tilt-rotor transport turned out to be more difficult and more expensive than anticipated, and last year the Obama administration cancelled the Expeditionary Fighting Vehicle, which would have given the Marines both enhanced amphibious assault capability but, even more important, more firepower and mobility ashore. The Marines' AV-8B Harriers- a development of the original British jump jet- are at the end of their service life, and the Marines' F-18s cannot operate from Marine amphibious assault ships. And there's hardly reason to have the big-deck amphibs without the F-35B. Conversely, operating a fifth-generation aircraft would give the Marine Corps a new viability in small-scale contingencies- think Libya- and allow them to contribute to more challenging "anti-access, area-denial" contingencies in East Asia or in an Iran-type operation. Similar challenges face the Navy; without a fifth-generation aircraft, its own aircraft carriers are increasingly irrelevant to high-end strike campaigns.

Ending the F-35 program would also eviscerate what remains of the American military aviation industry. Only two companies in the world have prime contractor experience in building manned "stealth" aircraft, Northrop Grumman and Lockheed Martin. Northrop's B-2 bomber, designed in the late 1970s, was last bought in 1997; only 21 of a planned 132 bombers. Northrop is no longer in that business. Lockheed built the F-117 Nighthawk, the first stealth fighter, another 1970s design and also long out of production. Lockheed also builds the F-22 Raptor, but that program was ended (with just 187 of a planned 750 aircraft produced) two years ago and the last F-22 will soon roll off the line. The F-35 line itself was sized (and the workforce planned) to build up to several hundred planes a year; under current plans, it's not going to reach maximum efficiency. Indeed, the company may have to lay off workers. There's no other place for the designers, engineers, or management to go; the investment, knowledge, and production experience to make stealthy, manned combat aircraft will rapidly disappear.

Of course, the two senators know all this; the letter is meant to pressure and publicly punish the Pentagon and Lockheed. But in this season of deficit, debt, and budget wrangling, politicians' posturing can have consequences. Former Defense Secretary Robert Gates already had placed the STOVL variant of the F-35 on two-year "probation." Gates also recently suggested- it was no surprise, really- that the new round of defense budget cuts introduced by the Obama administration (which have now risen from $400 to $500 billion in future spending, and are still rising) would result in fewer F-35s being bought. And with few other procurement programs left- across any of the military services- the F-35 is a big, juicy target for people wearing green eyeshades.

I thought that way once, more than ten years ago. As the principal scribe for the defense report of the Project for the New American Century, I argued that it would be preferable to buy more F-22s than to proceed with the massive F-35 program, which put so many eggs in a single basket with so many engineering problems still to be sorted out. But McCain and Levin are suggesting that we now do to the F-35 what was done to the F-22: terminate the effort with development and a tiny amount of procurement.

That's no longer a responsible choice or a realistic position. I've only outlined the consequences of terminating the F-35 and closer analysis would only reveal more problems. Loren Thompson of the Lexington Institute described the McCain-Levin letter as part of a "bad week for U.S. airpower." But it was more than that. The letter calls into question the future of American military power in its broadest sense.

Thomas Donnelly is a resident fellow and the director of the Center for Defense Studies at AEI