Aircraft

Flight International online news 14:30GMT: Although the sequence of events in the cockpit of the crashed Helios Airways Boeing 737 remains a mystery, earlier incidents have shown the crucial importance of reacting promptly to airliner depressurisations.

In both the incidents below the captain lost consciousness, leaving only the first officer flying the aircraft. And in both cases a flight attendant collapsed in the cockpit.

In this 1998 incident the highly experienced captain of a UK-registered Boeing 737 lost consciousness at 35,000ft when his oxygen mask became entangled with his spectacles as he tried to put it on. A flight attendant who tried to help him also collapsed.

Investigators found that a 17 year-old fatigue crack finally led to the failure of a cargo door at altitude.

And in this 1996 incident the captain of a Boeing 727 in the USA collapsed at 33,000ft when he delayed putting on his mask while trouble-shooting a pressurisation problem probably caused by human-error in using the system.

In this case the first officer’s problems were compounded by the fact that the flight engineer also collapsed and fell across the central console.

On both occasions the cabin emergency oxygen systems for passengers worked well and there were no casualties.

But masks can be donned very quickly, as this movie produced by Zodiac subsidiary Avox-Eros, which provides masks in some 737s, illustrates.