Rolls-Royce will temporarily replace any oil-leaking engines like the one that caught fire and blew apart on a Qantas superjumbo jet earlier this month, an aviation official said Monday.

Because airlines keep some spare engines on hand, the long-term impact to the Airbus A380 — the world's largest jetliner — and its buyers may not be dire, aviation analysts said. However, future deliveries of the A380 could be delayed if the scope of the oil-leak problem turns out to be greater than disclosed and a large number of temporary replacement engines are needed, they said.

Airbus spokesman Justin Dubon referred questions to Rolls-Royce, which manufactures the Trent 900 engines at issue, and added, "We're helping with the investigation and also to minimize disruption to customers."

Rolls-Royce declined to comment. Its stock, trading at 596.5 pence ($9.60) at Monday's close on the London Stock Exchange, has now lost 9 percent, or around $1.4 billion, since the Nov. 4 engine blowout that forced the Qantas A380 to make an emergency landing with 459 people aboard.

The airlines that fly A380s powered by the Rolls-Royce engines ran tests for leaks in the Trent 900, a lighter-weight motor designed to lift the four-engine superjumbo with less noise and fuel consumption. The engines cost an estimated $10 million to $11 million apiece.

Singapore Airlines replaced three Trent 900s. Lufthansa replaced one but said the reason was unrelated to the Qantas blowout.

Qantas said it found oil leaks in three of its A380s. Its entire fleet of six remains grounded since the blowout on the flight to Sydney, which forced the safe return of the jet to Singapore.

Qantas declined to provide details of its work on the engines but said it hoped to get its superjumbos flying again in days, not weeks.

"We are taking our normal and extremely conservative approach to safety and will not operate our A380 fleet until we are completely confident that it is safe to do so," Qantas spokesman Simon Rushton said.

Singapore Airlines said two of its 11 A380s were back in service and work was continuing on a third.

"We can't speak definitively about the number of engines that may ultimately require modification work as it needs to be stressed that investigations are continuing," Singapore Airlines spokesman Nicholas Ionides said.

Rolls-Royce had said Friday it would be replacing modules, or sections of linked parts, aboard Trent 900 engines with oil leaks, but it declined to provide details of what parts would be replaced or how the program would be carried out. Airbus said Rolls-Royce would also be equipping the engines with software to shut them down before an oil leak could cause an engine to disintegrate.

An aviation regulator told The Associated Press that Rolls-Royce would take off faulty engines and replace them with new ones. It will then fix the leaking part and swap the engine back again.

"They will take the rejected one, change the module in that one, and put it back into service," the official said. "In the meantime, they will replace it by a new one."

The official, who has been briefed by Rolls-Royce and some of the affected airlines, spoke on condition of anonymity because of the sensitivity of the matter.

The airlines are virtually certain to keep the Trent 900s on their superjumbos. Features such as fuel lines and software controls require a support structure on the plane that is designed specifically for that engine.

"It's not easy at all to change engines," says Richard Aboulafia, an aviation consultant with the Teal Group in Fairfax, Va. "You've got contractual problems, regulatory problems and engineering problems. It's easier just to replace the engine with a new and improved Trent engine."

He referred to the way planes are equipped with specific engines as "the razor blade model," a reference to safety razors that only accept matching blades.

Investigators say leaking oil caught fire in the Qantas engine on Nov. 4 and heated metal parts, causing them to disintegrate before the jetliner returned safely to Singapore. Experts say chunks of flying metal cut hydraulics and an engine-control line in the wing of the A380, causing the pilots to lose control of the second engine and half of the brake flaps on the damaged wing in a situation far more serious than originally portrayed by Qantas.

Qantas' six superjumbos are the backbone of its longest and most lucrative international routes between Australia and Los Angeles, Singapore and London. Further removal of engines could cause longer delays and potential revenue losses.

Airlines traditionally have spare engines.

"The issue is whether they have got significant numbers of engines to replace the number that are required," said Howard Wheeldon, a senior strategist at BGC Partners in London. "These things are not kept on the shelf.

"I think this is a slightly worrying move in that quite clearly the amount of time required to undertake such an exercise increases," Wheeldon said. "We could be talking many months rather than many weeks or many days."

That could lead to extended delays in getting the existing A380 fleet back in the air and potentially greater compensation claims from the affected airlines.

A longer replacement timetable — and using up spare engines — would also hit the delivery of all-new A380s due to Qantas, Lufthansa and China Southern Airlines in coming months.

Hans Peter Ring, chief financial officer of Airbus' parent company, EADS NV, said in a conference call with analysts Friday that "we cannot exclude that there is risk at this point."

"This is a very recent development, being managed on a daily or even hourly basis," he said.

British Airways, which in 2013 is due to receive the first of the 12 A380s with Trent 900 engines it has ordered, said it was not concerned at present.

Virgin Atlantic, which has six of the aircraft on order for delivery in 2015, said it will continue to monitor any ongoing discussions between the engine manufacturers and other operators.

Wheeldon said the direct expense of the work for Rolls-Royce would not necessarily be much greater than previously thought, given that the company was always likely to remove the entire engine to replace the faulty part.

Shipping spare engines to Australia would take roughly 24 hours at most, he said.

Lufthansa spokesman Thomas Jachnow declined to comment on any engine replacement, saying only that the company's engineers were in close contact with Rolls-Royce.

The airline is scheduled to take delivery of a fourth A380 on Tuesday. The plane underwent all the new tests mandated by the European Air Safety Agency last week, Jachnow said.

The next four A380 deliveries are scheduled for the first half of 2011, and Lufthansa expects no delays, he said.

Jachnow said the company has ordered a total of 15 A380s, all equipped with Trent 900s.

Separately, two of the affected airlines had what they described as minor mechanical issues Monday unrelated to the A380 engine problem.

An electrical fault sent smoke into the cockpit of a Qantas Boeing 747 about an hour into a flight from Sydney to Buenos Aires, Argentina, forcing pilots to turn back and land safely. It was the third time Qantas has aborted flights because of faults since Nov. 4. Qantas says the other issues were far less serious than the blowout and that the turnarounds were precautionary.

A Lufthansa A380 jetliner was stopped Monday shortly before takeoff for Tokyo because the pilot was worried whether its nose gear was functioning properly, a company spokesman said. The passengers left on another Lufthansa A380 five hours later, and no technical malfunction was found, said Lufthansa spokesman Andreas Bartels.


AP Airlines Writer David Koenig in Dallas and AP writers Juergen Baetz in Berlin, Julia Zappei in Kuala Lumpur, Malaysia, and Angela Doland in Paris contributed to this report.