SYDNEY - DRAMATIC mid-air engine problems on Qantas aircraft which forced two emergency landings in Singapore in as many days were unrelated incidents, a spokesman for the Australian airline said on Saturday.

A Qantas A380 superjumbo carrying 466 passengers and crew was forced to return to Singapore on Thursday after an engine exploded and failed during ascent, raining debris onto an Indonesian island.

And a Sydney-bound Boeing 747 turned back to Singapore shortly after take-off on Friday after reporting engine trouble, with one passenger saying she saw the affected engine sparking like fireworks.

Qantas spokesman Olivia Wirth said while both aircraft operated on Rolls Royce-manufactured engines, they were using different models and there was no apparent connection between the incidents.

'These are both unrelated incidents,' Ms Wirth told the Nine Network. 'They are unrelated.' Ms Wirth said travellers should feel 'absolutely safe' on Qantas, despite the recent run of problems, adding that the airline was investigating both incidents and was keeping its A380s grounded until they could be checked.

'Safety is at the heart of our business, we take these issues very, very seriously,' Ms Wirth said. Qantas has never had a fatal jetliner crash in 90 years.

Engine problems unrelated