British enginemaker Rolls-Royce has asked Airbus to return Trent 900 engines from A380 superjumbo production lines so they can be used to replace faulty ones on aircraft already in service. The Airbus A380 - the world's largest passenger aircraft with an average list price of about $350 million - has been hit by safety concerns after a Rolls-Royce engine partly disintegrated mid-flight, forcing a fully laden Qantas plane to make an emergency landing in Singapore on November 4.