The potential target: an American commercial jet.
The potential weapon: a shoulder-to-air missile that terrorists fire at the jet on takeoff.
Worldwide, at least 24 civilian aircraft have been brought down by shoulder-fired missiles, and more than 500 people have been killed. And experts say that shoulder-to-air missiles can be bought for only a few thousand dollars on the black market. But U.S. commercial aircraft still have no defense system against these portable missiles.
Last November, just minutes after takeoff from Los Angeles International Airport, an American Airlines pilot reported that something resembling a rocket might have been fired at his aircraft.
"American 612, can you verify whether you saw a flare or a rocket?" radioed an air-traffic controller.
"It looked more like a rocket to me," the pilot responded. "I'm pretty sure it was a rocket of some kind, because it had a definite plume coming out behind it."
The immediate concern was that the plume was in fact the trail of a shoulder-fired missile. The Coast Guard dispatched a cutter and a helicopter, and the FBI opened an investigation.
"We searched the area," said U.S. Coast Guard Lieutenant Clay Clary. "Nothing was found."
Although officials concluded it was most likely a hobby rocket, the investigation remains officially open.
"We had a scare in Los Angeles," said Sen. Barbara Boxer, D-Calif., who serves on the Senate Subcommittee on Aviation. "We've been told that they cannot rule out the fact that it was a shoulder-fired missile."
Although all the attacks to date have been on foreign soil, a potential attack on an American commercial jet remains a very serious concern. They say that an estimated 20,000 shoulder-fired missiles, most of them made in Russia, are for sale on worldwide black markets.
"It's a disaster waiting to happen," Boxer said.
The most recent attack was on a DHL cargo plane hit while taking off from Baghdad in November 2003. The plane managed to land safely with its left wing on fire.
In November 2002, an Israeli charter plane carrying tourists was fired at on takeoff from Mombasa, Kenya. The attack intensified Israeli efforts to equip its civilian aircraft against shoulder-to-air missiles.
"It was a real call for a real threat that was not very far from a real disaster that would have happened to an Israeli aircraft," said Israel Livnat, vice president of Israel Aircraft Industries and president of Elta Systems Ltd.
Last month the Israeli airline El Al began to equip its small fleet with anti-missile systems similar to those used on its military aircraft.
But in the United States, four years of warnings and congressional hearings and millions spent on feasibility studies have not led to an approved anti-missile system for commercial aircraft. The federal government still has no definitive plan to protect U.S. commercial aircraft, even though two companies have developed systems that they affirm will defeat the missiles.
While Congress has appropriated more than $200 million to develop and study the systems over the past three years, President Bush's latest budget requested only $4.9 million for the program, which some industry sources say could signal the end of its development.
"We are being irresponsible by not moving forward on this today," said Boxer.
There is even resistance from the airline industry, which says the airlines cannot afford the million-dollar systems needed to equip commercial jets.
Boxer said the potential costs to the aviation industry in the event of an attack would be enormous.
"We have a product here that works, and I would just say to the airline industry, they would sing a different tune if one of these missiles were fired, and it hit -- even if it didn't hit -- who is going to go in an airplane?" Boxer said.