A Christchurch Qantas flight bound for Melbourne has had to turn around not once, but twice.

Flight QF168 made two attempts to depart this morning and, after nearly five hours wound up back where it started, in Christchurch.

The Boeing 737-838 first took off at 6.46am before turning around above the Tasman Sea. It landed in Christchurch two hours later.

Flight QF168 from Christchurch to Melbourne has had to turn around not once but twice this morning. Image / Flightradar24

A Qantas spokesperson told the Herald: “Pilots elected to return to Christchurch due to an issue with their radio. The aircraft was inspected by engineering and has since taken off as normal.”

However, the plane’s progress was short-lived when Flightradar24 showed it turning around yet again as it approached the Tasman.

“Shortly after taking off again, an unusual smell was reported in the cabin.”

The pilots “followed standard procedures” and returned to Christchurch where the plane landed normally.

It is now back at Christchurch Airport.

“Engineers are inspecting the aircraft to determine the cause of the smell, and passengers will be reaccommodated on flights via Auckland today,” said the spokesperson.

“We apologise to customers for the inconvenience caused by these unrelated air returns, and are working hard to get customers on their way as quickly as possible.”

The plane has the registration VH-VZR and is 13 years old, Stuff reported.