Cathay Mayday was second on same plane

The Cathay Pacific plane forced to divert to Kazakhstan on Monday after losing cabin pressure made another emergency landing two months ago after a mid-air crisis involving a malfunctioning valve.

On September 11, the 21-year-old Boeing 747-400 - the oldest of its kind in the Cathay fleet - was forced to jettison fuel and return to London's Heathrow Airport an hour after taking off for Hong Kong when the cockpit crew realised a valve in the cabin pressurisation system had failed.

The valve was replaced and the plane took off again without incident. It remained in service before being forced early on Monday to declare an emergency and divert to Karaganda in Kazakhstan six hours into a flight from Amsterdam to Hong Kong.

Oxygen masks were deployed to 306 passengers plus the crew as the plane navigated mountainous terrain before a normal landing in Karaganda, to where a replacement plane was flown from Hong Kong to collect the passengers and crew early yesterday.

The cause of Monday's incident was a malfunction in another valve in the plane's cabin pressurisation system. Cathay Pacific last night said the two incidents involved different valves at opposite ends of the plane and were totally unrelated.

However, engineers are to carry out checks on valves in the cabin pressurisation system on board another of its 22-strong fleet of 747-400 planes to see if there are any problems that need further investigation.