US civilian planes 'shot down' four times a week in post-September 11 drills

The US military practises shooting down hijacked commercial airliners up to four times a week and has scrambled jets to intercept civilian flights more than 1,500 times - almost always on false alarms - since September 11 2001, it was reported yesterday.

The practice drills involve simulated hijackings on board chartered airliners filled with troops. Alarms sounded by the "squawk" buttons in the pilots' cockpit or deviations in the airliners' scheduled route are picked up in the headquarters of the North American aerospace defence command, or Norad. In the practice runs, the rogue planes are either intercepted by jets or shot down by anti-aircraft batteries on the ground.

After the first two airliners struck the World Trade Centre on September 11, the president authorised air force pilots to shoot down other hijacked planes. They scrambled too late to prevent the third passenger jet hitting the Pentagon, and the fourth plummeted into a Pennsylvania field before fighter jets reached it.

The head of Norad and the newly established northern command, air force General Ralph Eberhart, said the practice drills, carried out between twice and four times a week, were designed to ensure that any decision to shoot down a hijacked plane would be properly taken.

Authentication procedures are rehearsed to ensure "someone can't get on the radio and say: 'This is the president, I order you to shoot down that plane,'" Gen Eberhart told journalists. The drills are also aimed at ensuring that the pilots will be psychologically ready to shoot down a plane full of civilians.

"Before September 11 we never thought about shooting down a civilian plane," said a Norad spokesman, Major Douglas Martin. "We now talk with our pilots and tell them they need to have the nerve to pull that trigger."

Maj Martin said fighter jets had been scrambled 1,500 times since the September 11 attacks. Those incidents have almost always been false alarms. Emergency squawk buttons had been pressed by accident five times. But jets were also sent up to escort the airliner carrying the British would-be shoe bomber Richard Reid from Paris.

Gen Eberhart insisted that there was no chance a passenger airliner would be shot down accidentally. "I would take issue with anyone who would say the men and women in our armed forces are trigger happy," the general said. "I'm more worried that they would be trigger hesitant than trigger happy. We have long discussions with people to see if they're ready to do this."

He said he could not recall a drill in which a pilot or anti-aircraft battery officer refused to shoot down an airliner. He said the officers involved underwent extensive screening and continual tests to assess their readiness.

"The pilots are briefed; they are asked if they can do this," he said. "In the end, the pilots will save lives on the ground. But the pilots will have to live with this for the rest of their lives."