QANTAS is alleging in a multi-million-dollar damages claim against Rolls-Royce that it could now carry only 80 passengers across the Pacific in its Airbus 380s, under new operating rules for their troubled engines.

The airline states in Federal Court papers that it bought the Airbus superjumbos because they would carry 450 passengers and a payload of 60,900kg from Australia to Los Angeles.

Qantas: Passenger alerts crew after seeing fluid leak from wing

In pictures: QF32 damage

But the new rules imposed by Rolls-Royce since one of its Trent 900 engines exploded on a Qantas A380 near Singapore last month mean that the world's biggest passenger jet is not a commercial proposition on the airline's Australia-US route.

Qantas, which has suspended the route, has asked for damages and costs.

The national carrier is also seeking a declaration from the court ordering the UK engine maker to fund a $1 million credit note relating to a guarantee against "uncontained engine failure" - to stop engine parts perforating the outer shield of an engine.

Rolls-Royce is accused of negligence and breach of contract.

Qantas says in its statement of claim that Rolls-Royce continued to modify the Trent 900 engine, but left 23 engines on its big jets unmodified. At the time of the Singapore incident only one engine had been modified.

Meanwhile the nation's top air safety investigator has lauded pilots who landed the faulty Qantas Airbus in Singapore, saying they saved the lives of all the 469 people on board QF32 on November 4.

A preliminary report yesterday confirmed an oil leak as the most likely cause of last month's Qantas A380 engine failure over Indonesia's Batam Island.

The leak caused pieces of the Rolls-Royce engine to shear off, penetrating the aircraft's left wing and sections of the fuselage.

Capt Richard Champion de Crespigny and the four other officers safely landed the aircraft under the power of its remaining engines.

ATSB chief commissioner Martin Dolan said the cool-headed reaction of the pilots prevented a catastrophic accident.

"The aircraft would not have arrived safely in Singapore without the focused and effective action of the flight crew," he said.

Originally published as Jumbos reduced to 80 passengers