http://www.govexec.com/story_page.cfm?articleid=32992&dcn=e_gvet
Greta Wodele
"The Government Accountability Office estimates that more than 800,000 shoulder-fired missiles exist worldwide, with 27 terrorist groups known to possess them. The missiles are relatively cheap to purchase and take only seconds to prepare, require minimal training and have a flight time of three to 10 seconds. The missiles are most effective at 10,000 to 15,000 feet, when airplanes are taking off or landing and are at their most vulnerable altitude."
