Targeting airliners: aircraft missile defense: the debate continues.

The threat is said to be out there: a terrorist uses a shoulder-fired missile to take down a U.S. commercial airliner.

With up to a million man-portable missiles produced since the 1970s, questions remain as to how much should be done to protect U.S. commercial airliners.

These weapons "are a threat that we have to take seriously," Homeland Security Secretary Michael Chertoff told reporters recently.

In the wake of 9/11, Congress mandated that the Department of Homeland Security research long-term and short-term solutions to the problem. And while there are sharp disagreements over what the solutions should be, if any, industry experts concur that the threat should not be underestimated.

Clifford Lewis, president and chief executive officer of the risk management firm, Strategy X Inc., said the question is how does the threat compare to other scenarios, such as a terrorist again using jets as a weapon of mass destruction.

"There is no historical precedent for anyone using a shoulder-fired weapon in the continental United States," he said. That doesn't mean it can't happen, or that a U.S. airliner won't come under attack while flying into a foreign airport, he added.

"Is the threat real? Is it possible to do it? Of course, it is," Lewis said. "But where does that rack and stack with all the other threats?"

Since the 1970s, weapon manufacturers have produced more than 700,000 shoulder-fired missiles, some of which have fallen into terrorist hands, according to a 2005 Rand Corp. report, "Protecting Commercial Aviation Against the Shoulder-Fired Missile."

A commonly used term for these missiles is MANPADS, or man-portable air defense systems. They are relatively simple to use, compact, and therefore, easy to smuggle. That, put together with terrorists' proclivity to target commercial aviation, makes them a real danger, according to experts.

The State Department estimates that approximately 20 countries produce the technology, and puts the number of MANPADS manufactured since the 1970s higher at 1 million. "Several thousand" shoulder-fired missiles are outside the control of governments, it added.

Countering the domestic threat falls to the State Department, which is charged with proliferation issues, and the Department of Homeland Security's Customs and Border Protection agency, which must stop loose missiles from entering the United States. If their efforts should fail, and a terrorist succeeds in taking down a commercial airliner, the cost would be high, the Rand report notes.

Basing their analysis on the aftermath of the 9/11 attacks, the authors estimate direct costs of $1 billion for every aircraft shot down, with a potential of $15 billion in long-term economic impacts. Furthermore, "the perceived inability of the U.S. government to prevent attacks on its citizens on its own soil would set back U.S. efforts to counter terrorist groups globally and could weaken U.S. influence across a range of other interests abroad," the report said.

The costs for protecting the approximately 6,800 U.S. jet-powered airliners are also great, according to Rand. The think tank estimates an $11-billion price tag to install a single laser jammer on each U.S. commercial aircraft. Yearly operating and support costs would total $2.1 billion. The 10-year life-cycle costs could be as low as $25 billion if DHS can achieve its goals of creating an affordable system, or $40 billion, if it cannot.

Chertoff said this poses a philosophical question. "Is there a limit to the amount of cost you will pay to avoid a particular risk?" he asked. "The answer to that is always 'yes,' but the trick is to figure out what that limit is."

It is more than a philosophical question for the financially strapped airline industry, which will likely be asked to share the financial burden.

How much of the costs should be shouldered by the private sector and how much by the government is a "fairly complicated economic question," Chertoff said. "It's rarely going to be the case that all the costs are going to be borne by the government or all the costs are going to be borne by the private sector."

For now, the government is paying the research and development bill, and rightly so, Chertoff said. BAE Systems and Northrop Grumman received contracts of $45 million each for the research and development phase of the counter-MANPADS program. Phase three of the program began earlier this rear and will run through most of 2007. When that is completed, it will be up to Congress to decide whether it will proceed with funding, and who should pay for it.

John Meenan, executive vice president of the Air Transport Association, said, "only the government is in a position to determine the necessity for this kind of thing. But our sense is that there are probably better ways to deal with these kinds of threats."

The association has been one of the most outspoken critics of the counter-MANPADS initiative. Meenan called the effort "vendor driven."

"It has been much more driven by vendors interested in selling systems, without any real regard to where that stands in regards to the priority of the threat," Meenan said.

Steve DuMont, program manager of commercial airline protection systems at BAE Systems, refuted that assertion.

"I don't believe that this program is being vendor driven," he said. "It's being driven by the Department of Homeland Security's intent to further understand the suitability of this technology."

Meanwhile, DHS has said it is on track with carrying out the congressional mandate. Charles McQueary, the recently departed DHS undersecretary for science and technology, told the House Science Committee that the program will perform operational tests of the two competing systems this year. It will modify eight test aircraft, and launch nine different shoulder-fired missile systems against them, he said.

"The primary objective is to reduce the residual risk of operations in the commercial environment and lower the cost of ownership," McQueary said.

When asked how much of the costs for deploying counter-MANPADS units the airline companies should bear, Meenan said none of it.

"Resources are not without limit, and as a result, we need to be as smart as we possibly can be," he said. The ATA estimates the program's costs at $50 billion to $100 billion over a 20year cycle, which makes these figures higher than Rand's.

Still unknown is the cost to maintain these systems, Meenan said. The established failure rate for military counter-MANPADS units is around the 300-hour mark, he said. Military aircraft are generally not in the air as long as commercial aircraft, though. Commercial airlines look at 10,000-hour timeframes for system failures, Meenan said.

"What are the implications as far as maintenance time? What are the implications in terms of flight cancellations? What are the implications of storage of spares and parts around the world? None of that has been answered in any way," Meenan said.

There may be significant increases in fuel costs, and reductions in payload capacity because of the added weight, Meenan said.

DHS acknowledged the logistical challenges, noting that military aircraft operate out of a limited number of airports where access to spare parts is easier, while there are more than 400 facilities used by commercial aircraft in the United States. "The maintenance costs of counter-MANPADS technology at current system costs would be staggering," DHS said in a fact sheet.

Israel's national airline, El Al, is widely believed to be the first to install anti-missile technology on all its aircraft. However, the logistical burden for the relatively small carrier is minor since it flies from one airport hub.

DuMont said BAE Systems is working to answer all these questions. It has partnered with American Airlines' maintenance services and engineering division to work the logistical issues. BAE's proposed unit is designed to be swapped out within 30 minutes if faulty, and to minimize drag, which affects fuel costs.

"The airlines are operating on a razor-thin margin today," DuMont said. "Many of them are struggling to get out of bankruptcy. I think the last thing they need is another impact on added drag."

Lewis said Congress, and other stakeholders, will have two simple choices: find the money or accept the risk.

"But somebody is going to have to pay for it," he said.