Airbus's A380 superjumbo encountered fresh operational problems on Tuesday, when two aircraft had to abandon flights because of separate difficulties.
An A380 operated by Singapore Airlines and flying from Singapore to Frankfurt had to return to the Asian city state after one of its four engines developed a fault and had to be shut down. A superjumbo operated by China Southern Airlines ZNH and flying from Beijing to Guangzhou turned back to the Chinese capital after a malfunction with the air pressure system in the passenger cabin.
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These incidents follow an order by regulators last month for inspections of all 71 A380s that have been delivered to Airbus customers because of a wing cracking problem.
The European Aviation Safety Agency wants airlines to check for cracks on wing components and carriers including Emirates Airline, the largest A380 operator, are having to repair their superjumbos.
Singapore Airlines said one of its A380 flying from Singapore to Frankfurt with 430 passengers onboard turned back almost three hours into the flight after the crew reported a problem with one of the superjumbo's four Rolls-Royce Trent 900 engines.
The airline described the problem as a "surge", which typically involves a difficulty with airflow around the engine.
"We are looking into the incident and the engine will undergo thorough inspections in consultation with Rolls-Royce," said Singapore Airlines, the launch customer for the A380 in 2007.
Rolls-Royce said it was investigating the issue with Singapore Airlines. Airbus, the main subsidiary of EADS, the European aerospace group, declined to comment.
Of the 71 A380s that have been delivered by Airbus to airlines, 39 have Rolls-Royce's Trent 900 engines.
In November 2010, the A380 suffered its worst safety scare when one of the Rolls-Royce engines on a Qantas superjumbo exploded.
The aircraft had to make an emergency landing in Singapore and Qantas responded by temporarily grounding its entire A380 fleet.
Around the same time, Singapore Airlines grounded three of its A380s to replace some of the Rolls-Royce engines after finding signs of oil staining.
In December 2010, an investigation by the Australian Transport Safety Bureau found that an oil fire was the most likely cause of the Qantas A380 engine explosion.