The QF144 flight from Auckland to Sydney was flying over the Pacific Ocean on Wednesday afternoon, when crews started experiencing engine problems.

A mayday call was made, but later downgraded to a PAN (possible assistance needed), with the aircraft still on hour from its destination.

Paramedics and firefighters were deployed to the airport in preparation for a possible emergency landing.

"The aircraft landed safely at around 3.30pm and is now being inspected by our engineers," a Qantas spokeswoman said.

"While inflight engine shutdowns are rare, and would naturally be concerning for passengers, our pilots are trained to manage them safely and aircraft are designed to fly for an extended period on one engine.

The aircraft is a 10-year-old, twin-jet Boeing 737-800.

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"A mayday call is an internationally recognised, emergency or distress call," a spokeswoman for the Australian Maritime Safety Authority told AAP.

A mayday call is issued when a flight is in grave and imminent danger and needs immediate assistance.

Once the call is issued controllers alert aviation rescue, firefighting and emergency services with details on how to respond. They also provide assistance to pilots.

Federal Transport Minister Catherine King lauded the airline's safety record after a brief scare that had 100,000 people tracking the flight online.

"A relief to know that QF144 has landed safely," she tweeted.

"Well done to the highly experienced crew for getting the plane safely home.

"Australia's aviation industry is among the safest in the world because of the dedicated staff working on planes and behind the scenes."

The flight left Auckland at 2.30pm local time and landed in Sydney at 3.26pm.

with Australian Associated Press