Australian carrier Qantas on Friday diverted one of its A380s due to engine problems, a year to the day after a turbine blast, in the latest public relations setback after a shutdown grounded its fleet.

Flight QF31 was four hours into the flight from Singapore to London carrying 283 passengers and crew including British actor Stephen Fry when the pilot decided the oil pressure in one engine made it necessary to reroute to Dubai.

On November 4, 2010, flight QF32, also out of Singapore, experienced an engine blast en route to Sydney. That flight landed safely despite damage to the plane, but the incident prompted Qantas to ground all its A380s.

Qantas, which last week shut down its entire fleet over an escalating industrial dispute with unions, stranding thousands of passengers, subjected its Airbus A380 planes to intensive safety checks after the 2010 mid-air blast.

Qantas said there were no links between the two incidents. "This is a coincidence," spokeswoman Olivia Wirth said.

"It is an issue which has been detected in engine number four and it involves the pressure defect of the oil in this particular engine," she told reporters.

"It was shut down in line with procedures and the captain diverted the aircraft and safely arrived in Dubai around two-and-a-half hours later."

The aircraft was being assessed by engineers in Dubai, she added. "It will be a priority of ours to ensure that we work out exactly what the particular problem is in this engine," Wirth added.

Qantas said it was doing all it could to help passengers, including Fry who was amusing his 3.3 million Twitter followers with his remarks.

"Bugger. Forced to land in Dubai. An engine has decided not to play," was his first comment on the matter, adding two hours later while he was still sitting on the tarmac: "This plane, the crew tell me, is going nowhere."

Shortly after Tweeting that he was on a bus from the plane to the terminal he cut in with an expletive laden Tweet.

"I've left my wallet on the sodding plane," he said. "Hell's teeth this really isn't my day. Will not leave without it."

Which prompted this reply from Qantas' Twitter account: "Mr Fry, don't worry we will get your wallet back. We know the crew are keeping you updated and we are talking with them. So sorry."

The mid-air explosion in 2010 sent shards of metal raining down on an Indonesian island and punched a hole in the wing of the aircraft.

No-one was injured, but the emergency landing in a trail of smoke dented Qantas's reputation for safety.

Subsequent investigations pinpointed a manufacturing defect that caused fatigue cracking in an oil pipe, resulting in a fire and potentially catastrophic engine failure.

The incident prompted the replacement of dozens of turbines by airlines around the world.

Federal secretary of the Australian Licensed Aircraft Engineers Association (ALAEA), Steve Purvinas, said it was too early to say what caused the latest problem and he was surprised Qantas had said the two were unrelated.

"What amazes me is that Qantas can say this is unrelated to the QF32 incident from a year ago," he said. Qantas has 10 of the superjumbos in its fleet.

The latest incident came as Qantas chief Alan Joyce said legal changes being considered by parliament would threaten the firm's viability and cost jobs.

The airline boss was being grilled by a senate committee over proposed changes to the Qantas Sales Act, which seeks to ensure the airline remains Australian owned and controlled.

The inquiry was called after Qantas announced an Asia-focused restructuring in August, which has led to a bitter industrial dispute that culminated in Joyce grounding the airline last week.

Qantas services only returned to normal on Tuesday after an 46-hour shutdown that stranded 70,000 passengers in 22 cities worldwide.

Australian police said this week they were investigating the alleged sabotage of a Qantas plane, said by Purvinas to relate to the in-flight entertainment system.