VIENNA, Austria - They're light but lethal - and capable of bringing down a commercial jetliner within seconds.
Shoulder-fired, surface-to-air missiles similar to the ones involved in a sting operation last week are relatively inexpensive and chillingly easy to buy, said Jonathan Stevenson, an arms control analyst with London's International Institute of Strategic Studies.
"There are thousands of them out there, and they're fairly easy to procure - at least the cruder versions," Stevenson said.
"There are 4,000 to 5,000 of these missiles around Iraq. Africa is full of unregulated weapons left over from Cold War sponsorships and the Eastern Europeans are major league gun merchants. They're probably not a lot harder than buying a shotgun in places where there effectively is no government."
Experts say it's amazing the world hasn't seen more attempts to down airplanes.
One reason might be the rockets are rather conspicuous when being fired.
They also aren't very accurate, and they were designed to take out helicopters and smaller military aircraft, not jumbo jets with powerful engines. Egyptian forces fired hundreds of SA-7s at Israeli bombers during the 1973 Arab-Israeli war, and most of the bombers survived the assaults, which experts say might have discouraged wider use by terrorists.
The main threat to commercial flights has been hijackings - long, drawn-out affairs that guaranteed terrorists days of publicity without risking the kind of universal condemnation that mass murder would inspire.
But because airport security was tightened considerably after Sept. 11, some experts think terrorists might be rethinking the missiles.
The rocket at the center of Tuesday's arrest of British suspect Hemant Lakhani was a deactivated Russian SA-18 Igla missile. Weapons experts say the Igla is the most sophisticated, accurate and hard-to-get portable rocket.
But there are other choices for terrorists, including the American-made, Stinger shoulder-fired missile.
Intelligence officials say hundreds of Stingers are in Afghanistan, sent there by the U.S. government in the 1980s to help the Afghan resistance to Soviet occupation. Stingers also are commonplace in the former Yugoslavia.
Thousands of a class of missile known as the SA-7 Grail, also called the Strela, or Arrow, are in Russia. They have been produced in Russia, Eastern Europe, China, the former Yugoslavia, Egypt and other countries. Some have sold for as little as $500, according to U.S. intelligence.
"There's a considerable number of these sloshing about on the market. You can get the latest version or a 20-year-old rocket," said Wing Cmdr. Andrew Brookes, a weapons expert and a former reconnaissance pilot for Britain's Royal Air Force.
"The big question is how many of them have been bought by the bad guys. A dozen would do the trick for terrorists trying to achieve their main objective: to strike fear into the general population."