A Qantas aircraft's engine failed after the Boeing 747 left Sydney due to a technical problem known to the manufacturer, an air safety investigation has found.The Australian Transport Safety Bureau (ATSB) report also said the failure could happen again.But the ATSB says neither the airline nor the engine manufacturer were to blame for the February 2007 incident.The Los Angeles-bound Qantas flight had 274 people onboard and was at 4,000 ft when it was forced to return to Sydney Airport after the flight crew heard several loud bangs and felt vibration through the aircraft.The report found the manufacturer was aware of the issue with its engines and released a service bulletin in 2006 that provided design changes to help counter the fault.But even with the modifications, there was a possibility engine failure could still occur, as it had done in another airline, the report said.Qantas has increased its maintenance program to apply the modifications, but the task is not expected to be completed until 2010."From data gathered, the (engine) manufacturer determined that statistically there was a high probability of one further failure within their fleet before modification of all engines was completed," the report said.This is the fifth identical engine failure Qantas has experienced.Three of the five failures occurred on the same aircraft and another airline had experienced a similar failure 11 times, the report said. AAP