Washington (CNN) -- Fresh concerns that thousands of highly portable anti-aircraft missiles may be missing in Libya are prompting a new call to protect American jetliners from attack.
The fears that terrorists may have access to the Libyan missiles are revving up a decades-long debate over the vulnerability of American jetliners.
Sen. Barbara Boxer, D-California, wants to outfit hundreds of wide-body airliners with technology to protect the planes from terrorist attack. On Tuesday, she sent a letter asking the Departments of Defense and Homeland Security to establish a joint program to evaluate anti-missile devices and work toward their deployment.
"The risk to commercial aircraft posed by shoulder-fired missiles has long been acknowledged by the national security community," Boxer said in her letter to Defense Secretary Leon Panetta and Homeland Security Secretary Janet Napolitano. "Recent reporting of unaccounted for missiles in Libya is yet another reminder of this threat."
Cost estimates to outfit 500 airliners are $1 million per aircraft, adding up to $6 billion over the next 20 years.
One technology under consideration uses special sensors mounted on an airliner that would identify a threat, track an incoming missile and use a laser to trick the missile into changing course and missing the plane.
Boxer said in her letter that her goal is to protect more than 2 billion passengers over the coming 20 years. And she said additional work needs to be done on developing the reliability of the electronic countermeasures and how to resolve how the system can be exported overseas.
The concern has arisen anew since reports that some of Libya's 20,000 man-portable air defense systems, or MANPADS, have gone astray in the midst of the revolution and the toppling of the regime of Moammar Gadhafi. And many tens of thousands more exist around the world.
A State Department report in July called the proliferation of these weapons a threat to both national security and passenger air travel.
Some of these portable weapons can be carried and launched by one person, while others may require several people. They can be as light as 28 pounds and easily hidden in the trunk of an automobile.
"Because MANPADS are easy to transport, conceal, and use -- and because a single successful attack against an airliner would have serious consequences for the international civilian aviation industry -- they are particularly attractive weapons to terrorists and criminals," the State Department report said. "Keeping MANPADS out of their hands is thus a major priority for the U.S. government."
After CNN's Ben Wedeman reported on a looted weapons warehouse near Tripoli in early September, Homeland Security Secretary Napolitano said the threat had not been raised to her.
"If it becomes a risk, it will be raised to me. And as of today, it has not been raised to me. That doesn't mean that tomorrow it won't be raised to me. But as of today, it has not been raised to me," Napolitano said.
Napolitano said the Transportation Security Administration already certifies international airports where planes leave for U.S. destinations after a MANPAD evaluation.
Previous discussions about equipping airlines got caught up in disagreement about who should finance the cost of furnishing airlines with the system: airlines or the government. Airlines opposed mandating the systems because the companies did not feel that the threat warranted the cost, according to an industry representative who would speak only on background. Aircraft are vulnerable to the missiles for only a relatively brief portion of the flight: takeoffs and landings.
Airlines also raised concerns about the weight of the system and effects on revenues, as well as delays and disruptions to flights that would arise from mechanical problems from the system.
White House Press Secretary Jay Carney said Tuesday that the U.S. was working with NATO and Libya's Transitional National Council on the proliferation is of conventional weapons from there.
"The potential for conventional weapons proliferation from Libya has been of concern for many years," Carney said. "Since the beginning of the crisis, we have been actively engaged with our allies and partners to support Libya's effort to secure all conventional weapons stockpiles, including recovery, control and disposal of shoulder-fired anti-aircraft missiles."
The State Department says MANPADS have hit 40 civilian airliners since 1975, resulting in 28 crashes and 800 deaths.
Although Libya has ratcheted up concerns about portable anti-aircraft missiles, many observers say it is just a reminder of a larger global problem.
"The black market cost of MANPADS can vary widely, ranging from as little as a few hundred dollars to over one hundred thousand dollars, depending on the model and its condition," the State Department report says. "Given the relatively low cost of some of these systems, there is a heightened risk for acquisition by terrorists or other non-state actors."
And since 2003, the State Department says, the U.S. has managed to buy, or locate, and destroy more than 32,500 MANPADS in more than 30 countries.