`Collision warning system was off'

ZURICH (Switzerland) JULY 3. A collision warning system at the Zurich airport was out of service for maintenance when a Russian charter jet and a cargo plane rammed into each other at an altitude of 10,500 metres while in Swiss air space, officials said on Wednesday.

Further, an official for the air traffic control company said, only one controller was working in the tower at the time of the collision — despite regulations that two workers must always be on duty when the collision warning system was not active. The official said the second controller had taken an unauthorised break.

Patrick Heeb of the Swiss air traffic control company, Skyguide, said the warning system, designed to sound an alarm when there is danger of collision, was undergoing software checks. The maintenance is typically done during periods of light air traffic. Monday's collision happened shortly before midnight.

Mr. Heeb refused to say whether the system might have helped prevent the two aircraft smashing into each other over southern Germany at 11:35 p.m. as both descended to avoid colliding. Seventy-one people, the majority of them Russian schoolchildren heading for vacation in Spain, were killed.

Skyguide said on Tuesday the lone Zurich tower controller gave the Russian crew just 50 seconds warning to dive, even though the danger should have been apparent much earlier. The Swiss originally claimed to have given the Russian pilot two minutes' warning.

The Russian pilot responded only on the second request — 25 seconds before the collision. At the same time, the DHL cargo plane also descended in response to an onboard collision warning alarm.

``There seems to have been an extraordinary combination of extremely unlucky coincidences,'' said Mr. Heeb.

Investigation officials hoped to be able to interview the air traffic controller — who has not been named. He was treated for shock on Tuesday. The man has been described as an experienced controller.Skyguide said a second controller had broken regulations by taking a break at the time of the collision.

— AP

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