Armed federal law enforcement agents posing as passengers will be the norm on domestic and international airline flights in the wake of the four hijackings. Airline pilots say passengers must now serve as the last line of defence against suicidal terrorists.

The Federal Air Marshal Program, involving an undisclosed number of US Federal Aviation Administration agents trained to foil air piracy, is being augmented by law enforcement officers from the US justice department. The new sky marshals will undergo instruction at the FAA's technical centre where FAA agents are trained for anti-hijacking missions.

The cabin security programme began in the 1970s to prevent hijackings to Cuba, but few of the elite personnel are operational.

The marksmen are trained to fight in the confined space of an airliner cabin. Exercises are conducted in a mock air traffic control tower and in retired Boeing 727s and Lockheed L-1011 TriStars. Hollow-point, grooved aluminium ammunition is carried that will not penetrate the aircraft skin or damage aircraft systems.

Source: Flight International