As many as 40 Rolls-Royce engines fitted to Airbus A380 superjumbos may have to be replaced following the mid-air explosion on a Qantas flight earlier this month.Rolls said last week that one component in the turbine area had caused an oil fire in the Trent 900 engine, creating an explosion. But the Australian airline thinks almost half the Trent 900s used by Qantas, Singapore Airlines and Germany carrier Lufthansa will need to go.Chief executive Alan Joyce says three engines on his six A380s - which have four engines each - have already been replaced and that the final figure for the entire fleet of planes will be around 40."We'll have a daily dialogue with Rolls-Royce to determine which engines actually need to be taken off," he said. It's thought the final figure will be about 14.That raises questions about when the Qantas A380s will fly again. They've been grounded since the blast over Indonesia forced an emergency landing in Singapore.Singapore Airlines, which has grounded three of its eleven A380s, has replaced three Trent 900s, while Lufthansa, which flies three of the planes, has replaced one. Emirates and Air France don't use Rolls' engines on their A380s.