Qantas Airways is reviewing the way it operates its A380s after last week’s engine blowout, a source said on Tuesday, amid reports the carrier worked its Rolls-Royce engines harder than rivals.

Qantas’s use of its A380 engines is being looked into as part of a wider investigation into why a Rolls-Royce Trent 900 engine blew apart last week forcing an emergency landing in Singapore, an airline source told Reuters on Tuesday.

“The operations are one of the things Qantas are reviewing along with the components,” the source said.

The Australian newspaper reported Qantas operated its A380 engines at higher maximum thrust levels than rivals, which could result in resonating vibrations that cause oil lines to crack.

The higher thrust setting is used on some Qantas A380 take-offs on long-haul routes between Los Angeles, Sydney and Melbourne, the daily said, quoting unnamed engineers. The thrust setting of 72,000 pounds remained 3,000 pounds below the engine’s design limits and within operating guidelines, it said.

Qantas chief executive Alan Joyce said on Monday that while its engines had a “slightly higher level of power” than those used in Lufthansa planes or Singapore Airlines, they were certified to operate at those levels.

Jeff Jupp, a fellow of the Royal Academy of Engineering and former Airbus technical director said: “These engines go through a lot of testing before they go into service and I am certain Rolls would have run the engine at thrust levels about 10 percent higher than they are put it into service at.

“It is possible that Qantas may have been running the engine at closer to its limits than the other airlines, hence they have had problems with wear before the other carriers.”

Rolls-Royce moved to contain a crisis of confidence in the safety of its engines on Monday, saying progress was being made in finding out what caused the blowout.

Rolls-Royce shares continued to reverse losses after last week’s 10 percent drop and were up 1.8 percent by 1150 GMT. The stock closed 2.7 percent higher on Monday after saying the engine failure was not part of a wider problem in its family of Trent engines.

Qantas shares closed 1.8 percent lower at A$2.75. The stock is down about 5 percent since the incident.

Qantas, which declined to comment on the report, had said on Friday it suspected a material failure or a design issue may have caused last Thursday’s engine failure over Indonesia which forced an emergency landing in Singapore.

“I do not think it is a major problem with the architecture of the engine or its family derivation and is more likely to be a detail design problem with a bearing or seal” said Jupp.

“I suspect it is associated with the wear and tear in service because these engines have done about 8,000 hours — significantly longer than any engine on test runs.”

FINANCIAL IMPLICATIONS

Qantas’s A380 planes account for about 7.5 percent of its seat capacity, according to analysts. JPMorgan analyst Matt Crowe estimated that a week on the ground would cost the airline A$15-A$20 million ($15-$20 million) in revenue.

The impact was expected to be below that caused by a volcanic ash cloud in April which forced Qantas to cancel Europe-bound flights for around two weeks and had a A$46 million hit on its profit.

“While the potential cost implications — customer replacement capacity, rectification and upgrades — of this are impossible to predict at this stage, the relatively small size of the (A380) fleet would suggest, whatever the outcome, that it is containable at group level,” said Investec analyst Andrew Gollan, adding the investigation would likely take “weeks rather than days” to complete.

The airline was hit with a further setback on Monday night when a violent storm grounded some flights out of Sydney.