Two Qantas pilots were suspended on Wednesday after forgetting to lower landing gear as they came in to land at busy Sydney airport.
The Boeing 767 was just 700 feet above the ground when alarms went off alerting the pilots the landing gear had not been deployed.
The undercarriage is normally lowered at between 2,000 and 1,500 feet.
The pilots immediately boosted power to the engines to regain altitude and flew around the busy airport before coming in to land safely.
The airline today issued a statement saying the events around Monday's flight from Melbourne constituted a "serious incident" and would be subject to a full investigation by Qantas and the Australian Transport Safety Bureau.
"This is an extremely rare event but one we have taken seriously," the Qantas statement said.
"The flight crew knew all required procedures, but there was a brief communications breakdown. They responded quickly to the situation and instigated a go-around. The cockpit alert coincided with their actions."
The cockpit alert was an audible warning from the ground proximity warning system.
Qantas said there was no issue of flight safety, and the airline was fully cooperating with the investigation.
The Australian Transport Safety Bureau is also investigating an incident on a Jetstar Airbus A330-200 flight Saturday from Tokyo to the Gold Coast, which experienced a speed-sensing problem similar to one linked to the June crash of an Air France jet in the Atlantic Ocean off Brazil.
The autopilot on the Jetstar plane disconnected after a sensor measuring airspeed may have iced up, causing a false speed reading as the plane flew through a storm.
The pilots took control and the 200 passengers were unaware of the problem as the plane landed without incident.