Australia's national carrier Qantas has sought to reassure passengers of its fleet's safety after enduring a third successive day of mid-air issues.
A QF430 flight returned to Melbourne's Tullamarine Airport some 10 minutes after departing for Sydney on Friday morning, turning around near Bonnie Doon and touching back down safely.
In a statement, Qantas said the Boeing 737 returned as a precaution after the pilots were alerted to a minor engine issue.
"Customers will be reaccommodated on the next available flights over the next few hours," it said.
"The aircraft landed normally - this was not an emergency or priority landing. Both engines remained operational throughout the flight."
Soon after, Canberra-bound QF1516 turned back to Melbourne as a precaution over an issue with its flaps. Customers were again transferred to a new aircraft.
The incidents come after a Qantas service from Auckland to Sydney issued a mayday following an engine shutdown on Wednesday and another service from Sydney to Fiji on Thursday turned back over potential mechanical troubles.
Transport safety investigators have since confirmed they will analyse the Auckland to Sydney flight's cockpit voice recorder and flight data after the engine failure.
More than 10,000 air turnbacks occur across the aviation industry each year, with Qantas accounting for about 60 of those on average.
There are an estimated 400 to 500 engine shutdowns in narrow body jet aircraft across the globe each year.
Qantas Domestic chief executive Andrew David said it was important to keep things in perspective, declaring diversions and air turnbacks happen every day for a range of reasons.
"They usually reflect an abundance of caution and that's why flying is such a safe way to travel," he said.
"We understand that when you hear reports of planes turning around, it's concerning. But people can be assured that aviation is built on safeguards, and one of those safeguards is that if something isn't right, we take a conservative approach to the problem rather than pressing on.
Mr David said aircraft are complex pieces of machinery with millions of moving parts, and it's not uncommon to have a problem with one of them.
The Australian and International Pilots Association declined to comment on the latest incidents.