A QANTAS plane from Bali to Sydney has made a sudden landing in Broome after encountering an electrical fault mid-flight.

QF44 left Ngurah Rai International Airport in Bali around 10.40pm last night but ran into a problem about halfway through the six-hour flight.

Pilots requested priority landing in Broome, 3000km from its intended destination in Sydney.

A Qantas spokeswoman told news.com.au the landing was forced due to an electrical fault.

"A Qantas flight from Denpasar to Sydney diverted to Broome in the early hours of the morning as a result of an electrical fault," the spokeswoman said.

"The aircraft landed safely, and we're working with Broome airport to disembark passengers and re-accommodate them onto alternative flights."

The incident comes a day after a "loud bang" was heard on a Qantas flight from Tokyo to Cairns, with frightened passengers saying they saw orange flames and sparks coming from outside the plane.

The Boeing 747 made an unscheduled landing in Cairns after pilots discovered an issue with one of the engines in the early hours of Sunday morning.

Qantas fleet safety captain Debbie Slade said the engine was shut off by the pilots in line with standard procedures and there was no risk to passengers despite their concerns.

"While customers may have heard a loud bang, there was never a safety risk with the flight. These aircraft are designed to safely operate on three of the four engines," Ms Slade said of Sunday's incident.