The lawmakers said anti-aircraft missiles -- such as the US-made Stinger and the Russian-made SA-7 -- can down a plane several kilometers (miles) away and as high as 3,600 meters (12,000 feet).

But they said passenger planes now can be outfitted with new technology that can detect the source of a missile, jam its guidance system and steer it off its flight path.

California Senator Barbara Boxer, was one of four legislators at a press conference in the Senate Wednesday, raising the alarm about the portable weapons, which are available on the black market for between 25,000 and 80,000 dollars apiece.

"Most of these missiles require very little training and they take just a few minutes to fire," Boxer said.

Legislators propose adding 30 million dollars to begin the process of arming commercial jets with anti-missile defenses, to be added to the 75 billion dollars in emergency funds requested by the White House to pay for the war in Iraq.

Legislators have given greater attention to the issue after a failed attack last November, when a terrorist fired a shoulder missile attack on an Israeli-owned jetliner leaving Mombasa, Kenya.

Boxer said members of the al-Qaeda terror network are suspected of having targeted US military planes in Saudi Arabia last May with an SA-7 missile.

"Al-Qaeda has shown that it is willing to use these weapons as weapons of terror," said Boxer.

Republican Representative John Mica of Florida said the issue came to his attention several weeks ago during a closed door hearing at the House of Representatives.

"I went in to the meeting somewhat skeptical. I cam out convinced that this is probably one of the most serious challenges that we face" in combatting terrorism, said Mica, chairman of the House aviation subcommittee.

"Since that hearing, I have lost some sleep and have great concern," he said.

Mica estimates it would cost between one million and two million dollars to equip each aircraft with the the defense systems.

New York Democratic Senator Charles Schumer said it is hard to overstate the danger.

"If you had to make a list of what ar the greatest threats that could do the most damage to our country, shoulder-held missiles are at the very top of the list," he said.

"Unfortunately, our military made these easy to use for the purpose of good, and terrorists can find them easy to use for purposes of evil," he said.

The funds would to added to a massive package to aid the struggling airline industry, which is reeling from the stagnant economy, the effects of the war on Iraq and the staggering costs of additional security measures prompted by the domestic war on terror.

The House Appropriations Committee on Tuesday approved 3.2 billion dollars in support for the airlines, while the Senate committee supported allotting 2.7 billion dollars in direct aid and 800 million for "war insurance."

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