Four emergency landings no big deal, Qantas chief says

"We have low levels of turnbacks compared to most of the world fleets," head of Qantas Alan Joyce says. File photo / Andrew Labett

A fourth Qantas plane has been forced to turn back mid-flight, marking the second day of technical difficulties for the national carrier.

The Boeing 717 was forced to turn back 20 minutes into its flight from Hobart to Melbourne at 6.30pm on Tuesday after an indicator light in the cockpit reportedly went off.

The Boeing 717, which holds 110 passengers, is being assessed by engineers in Hobart, the ABC reports.

It was the fourth time in two days a Qantas plane had been forced to make an unscheduled landing.

Qantas chief Alan Joyce earlier played down the recent aircraft troubles, saying such events "happen all the time".

"We have really high reliability. We have low levels of turnbacks compared to most of the world fleets," Mr Joyce told reporters.

On Tuesday an unplanned landing involved a Qantas flight on the way to Dallas.

About four hours into the flight, the aircraft was turned back to Sydney because of problems with the in-flight entertainment system and troubles with some of the toilets.

Earlier, two planes made unscheduled landings at Perth Airport because of an unusual odour, a faulty warning system and issues with the air-conditioning system.

Mr Joyce says airlines turned back "thousands upon thousands" of flights across the globe every year because of issues affecting passenger comfort and safety.

Turnbacks on Qantas planes occurred at a rate of about half the global average, he said.

He dismissed as "absolute rubbish" suggestions that offshore maintenance was behind the troubles.

Mr Joyce said Qantas was the only carrier in Australia to still carry out maintenance in Sydney and Brisbane.

He apologised to customers who were inconvenienced by the turnbacks, and said the company had gone out of its way to minimise disruptions by putting on extra planes and paying for hotels.

- AAP