SYDNEY (Australia) - QANTAS Airways said on Thursday it will financially compensate all passengers who were on board a plane that made a terrifying plunge this week, tossing people around the cabin and injuring dozens.

Every passenger will receive an airfare refund and a travel voucher equal to the cost of a flight between Australia and London, a Qantas spokesman said.

The airline also planned to help pay medical expenses for injured passengers, said the spokesman, speaking on condition of anonymity because of company policy.

More than 40 people were taken to hospitals, with 14 seriously injured, after the A330-300 briefly plunged nose-first during a Tuesday flight from Singapore to the western Australian city of Perth.

Qantas, which has been beset by a string of safety problems in recent months, said it was cooperating with an investigation by the Australian Transport Safety Bureau and also conducting its own.

Bureau investigators said on Wednesday that instruments aboard the A330-300 warned pilots of a glitch in the stabilisation system just before the sudden altitude changes.

The agency said it was too early to determine the specific cause of the accident, but that it would issue a preliminary report on it within 30 days.

A preliminary review of the flight data recorder indicated the plane climbed about 60 meters from its cruising level of 11,000 meters and then went into a nose-dive, dropping about 200 meters in 20 seconds, before returning to cruising level, the safety bureau said in a statement.

The sharp drop was quickly followed by a second nose-dive of about 120 meters in 16 seconds.

'It was horrendous, absolutely gruesome, terrible, the worst experience of my life,' said passenger Jim Ford, of Perth.

He said he thought he was about to die as he watched unbelted passengers being flung around the cabin.

The plane, carrying 303 passengers and 10 crew, was nearing its destination when the incident occurred. It made an emergency landing in Learmonth, Western Australia, about 1,100 kilometers northeast of Perth.

Passengers who were not wearing seat belts flew into the air, some hitting the ceiling of the plane. Loose items scattered throughout the cabin and some overhead luggage compartments flew open.

It was the latest in a string of safety issues to plague the Australian airline since one of its planes was forced to make an emergency landing in the Philippines in Jul after an oxygen tank exploded on board, ripping a gaping hole in the fuselage.

Other problems since then included a loss of hydraulic fuel that led to an emergency landing on one flight, a failure of the landing gear on another, and detached panels on various planes, all of which prompted a review by the Civil Aviation Safety Authority.

The review found 'signs of emerging problems' in the airline's maintenance of planes, and CASA ordered Qantas last month to improve.

Qantas had previously been known for its strong safety record, having never lost a jet to an accident. It lost a smaller plane in 1951. -- AP