WEAPONS that fire high-intensity "sonic bullets" could be used by sky marshals to incapacitate terrorists who try to hijack passenger aircraft. The US Department of Defense is assessing the technology following the attacks on 11 September.

Elwood Norris, chairman of American Technologies in San Diego, California, says the Department of Defense approached him about a device the firm has patented that produces narrow but high-power beams of sound. Norris says the device could be used on hijackers to inflict pain and possibly disorientation. "They wanted to know, could you use this without any destruction to fuselage walls and windows? And the answer is yes," he says. A key defence contractor, cruise missile maker General Dynamics of Falls Church, Virginia, is funding development of the system and is helping AT to brief the Army and the Pentagon on its capabilities.

Norris's device, which he calls a "directed stick radiator", is encased ...