A former Qantas pilot says the mayday call issued during a Auckland to Sydney flight was surprising and might impact the aviation industry.
Qantas flight QF144 issued the emergency warning about 2:30pm Sydney time yesterday mid-flight, after one of two engines on the Boeing 737-800 failed.
That alert was later downgraded to a "PAN" (possible assistance needed) and the plane landed safely at Sydney airport, where it was met by dozens of ambulances, police and fire and rescue crews.
All 145 passengers disembarked safely.
Qantas says its engineers are investigating what went wrong, but a former pilot for the national carrier told the ABC the mayday call was "interesting".
"Normally you don't do that, the idea is that you're in great imminent dangers like you're about to die ... it's unusual they would have done that," said Keith Tonkin, the managing director of Aviation Projects.
"They must have been very concerned about the circumstances."
Another former Qantas captain, Peter Bates, said the pilot may have had to shut down the engine as a precaution if it exceeded its operational limit.
"It was obviously of concern to the crew however it was a very managed process," he said.
"The pilot would need to secure the engine and prevent it damaging itself ... then select an appropriate altitude and speed to continue the flight onto Sydney."
After disembarking, passengers told the media the crew kept the atmosphere on board calm and professional and didn't inform them of the engine failure.
Some said they heard a little "bang" during the flight and felt some light turbulence but there was no announcement from the flight deck.
Mr Bates said the captain may have decided not to alarm the passengers if the incident wasn't deemed critical enough.
Qantas said they would share more information about what happened after the plane had been assessed by engineers.
Mr Tonkin, who has years of experience of flying the Boeing 737-800, said the findings could have consequences for the entire industry.
"There'll be a lot of interest in what happened and why to understand if there's an implication for the broader fleet," he said.
"I don't know anything that could have caused that off the top of my head."
The Boeing 737-800 is one of the most popular aircraft in aviation history and used by airlines all around the world.
Mr Bates said pilots practise for a single engine failure at least four times a year and would be well prepared.
"The simulator simulates the airplane extremely well and quite often when something like this happens in reality [pilots] reflect on the level of difficulty in the simulator."
"The simulator is harder to actually manage and fly than an airplane."
Qantas said while in-flight engine shutdowns were "rare", aircraft were designed to fly for an extended period on one engine.
Mr Tonkin said it would mean the captain couldn't fly as high, fast or far and could have difficulty landing if there was a crosswind.
"It would have been relatively startling … but normally it's a matter of identifying what the problem is and then working out how to solve it."
Just two weeks ago Qantas was named the safest airline in the world — a title they lost last year after dropping to seventh place.
