Terrorists may seek to down aircraft by shining powerful lasers into cockpits to blind pilots during landing approaches, federal officials are warning in a bulletin distributed nationwide.
The memo sent by the FBI and the Homeland Security Department says there is evidence that terrorists have explored using lasers as weapons, though there is no specific intelligence indicating al-Qaeda or other groups might use lasers in the US.
"Although lasers are not proven methods of attack like improvised explosive devices and hijackings, terrorist groups overseas have expressed interest in using these devices against human sight," the memo said.
"In certain circumstances, if laser weapons adversely affect the eyesight of both pilot and co-pilot during a non-instrument approach, there is a risk of airliner crash," the agencies said.
In September a pilot for Delta Air Lines reported an eye injury from a laser beam shone into the cockpit during a landing approach in Salt Lake City. The incident occurred about 8km from the airport. The plane landed safely.
FBI and other federal officials are investigating. It is not clear if a crime was committed or if the laser was directed into the cockpit by accident. Steve Luckey, a retired airline pilot who is chairman of the Air Line Pilots Association's national security committee, said pilots are concerned about a recent increase in laser incidents, but do not know what to make of them. He said he has learned of two or three cases in the past 90 days.
"The most recent incidents appear to be aimed at pilots in the vicinity of airports," Luckey said. "A few seem to be intentional, and we're wondering why and what's going on."
Lasers can cause temporary blindness and severely damage the eye by burning the retina. The bulletin notes they are "relatively inexpensive, portable, easy to conceal and readily available on the open market."
Lasers are commonly used in a number of industries and are featured in outdoor light shows. A variety of more powerful military-grade lasers are produced around the world, but there is no evidence that terrorist groups have managed to obtain one, according to federal officials.
The bulletin was sent late last month to law enforcement officials and key government agencies and industries.