Flight QF706 left Adelaide at 6.12am and landed safely in Melbourne just after 8am, with the pilots following procedure and descending to 10,000 feet to stabilise pressure in the cabin.

Customers left the plane normally and were to be transferred to other flights, a Qantas spokesman said.

The aircraft would be examined by engineers in Melbourne to determine the fault, he said.

"We would like to thank our customers who followed the crew instructions and remained calm during the diversion."

A passenger took to Twitter to describe the incident.

"QF706 to Canberra this morning lost cabin pressure so we put the oxygen masks to good use while diverting to Melbourne," Greg Denehy wrote.

"Kudos to the professionalism of the Qantas crew with the safety and wellbeing of passengers clearly the priority. Not how I expect my morning to go though."

The Australian Transport Safety Bureau said it was aware of the incident and would "gather information".

"The ATSB can confirm it has been notified of an occurrence [on Tuesday] where a Boeing 737 on a flight from Adelaide to Canberra diverted to Melbourne due to reported pressurisation issues," a spokesperson said.

The ATSB will gather information into the occurrence before making a decision on whether or not to formally investigate.