No one is sure exactly how many commercial aircraft have been brought down by these missiles. Between 1975 (when the missiles first began to show up on the black market) and 1992 (when the last known incident of an aircraft being downed), between 29 and 40 commercial aircraft were shot down. Between 550 and 700 people were killed. The uncertainty arises from the fact that nearly all these aircraft were lost in Africa, or other out of the way places where the exact cause of an aircraft crashing could not be confirmed. All the aircraft were smaller, two or three engine commercial types, usually quite old.
There are thousands of portable missiles, particularly the Russian SAM-7 (and some later versions) on the black market. While the SAM-7 is still made, many of those available to terrorists are old and basically useless. Some later model Russian missiles have been recovered in anti-terrorist raids, and some of these have become inoperative due to age or poor handling. There are still some American Stinger missiles from the 1980s Afghan war out there, but their batteries have long since died, rendering the missiles useless.
Perhaps as many as a dozen Russian made missiles have been fired in Iraq in the past year. Two aircraft were hit, but were able to land. Its uncertain exactly how many missiles were fired because several are known to have been duds (because of missile parts found), and other duds have probably not been found. So the missiles are still a threat, but not a large threat, at least judging by the damage these missiles have actually done in the last decade.
While there have been no recent incidents of portable surface to air missiles (SAMs) being used in Iraq or Afghanistan, the danger remains. As a result of that danger, the U.S. Air Force has all 105 of its C-17s and 500 (90 percent) of its C-130s equipped with missile detection and countermeasures systems. A few of these countermeasures use lasers or infrared light, which blind the heat seeker on the missile. Most countermeasures, however, use flares, which draw the missile away from the aircraft using their high heat. The most modern missiles are not fooled by the flares, which is why the more expensive laser and infrared based systems are preferred. These defensive systems cost between one and four million dollars per aircraft, and weigh between 300-500 pounds.