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Air safety investigators say they will look into claims signals from the base used to communication

with US and Australian ships and submarines may have interfered with the Qantas Airbus's computer.

During the emergency the plane plunged 650 feet in seconds, injuring more than 70 passengers and crew.

The naval communications base is at Exmouth in Western Australia’s north, 30km from where the Qantas Airbus A330-300 made an emergency landing at Learmonth last week.

There were 303 passengers and 10 crew aboard when the plane suddenly dropped altitude, hurling people around the cabin and forcing the pilot to land.

The Australian Transport Safety Bureau today said it would examine whether powerful electromagnetic signals from the communications base could have sparked the emergency.

The base uses powerful low frequency radio transmissions to US Navy and Australian Navy ships and submarines.

It is understood to be the most powerful transmission station this side of the globe and includes 13 radio towers, the tallest of which is 387m tall.

The base is named the Harold E. Holt communications station after the former Australian Prime Minister.

ATSB spokesman David Hope confirmed the new line of inquiry today, after "several" groups had raised it as a possibility.

"We're looking at everything as part of a very thorough investigation," Mr Hope said.

"That's been raised by a number of people to say that somehow or another this US military base has got a very high frequency signal tower there and that could somehow interfere with electrical devices - so we'll look at it."

The latest possibilty comes as the world's Airbus operators were warned urgently of the autopilot failure.

The ATSB has already found that the Airbus A330-300's air data computer - or inertial reference system - sent erroneous and spike information to the flight control computer causing the autopilot to disconnect.

The aircraft was cruising at 37,000 feet when the fault occurred, causing it to descend up to 650 feet in seconds.

Last night, the Australian Transport Safety Bureau (ATSB) said it was likely a fault in the Airbus A330-300 jet's inertial reference unit was the cause of the incident, and it was likely to be a "unique event".

Investigation director Julian Walsh said the faulty unit continued to feed "erroneous and spike values'' to its primary computers.