An investigation is under way into how an AirAsia plane and a Jetstar plane came dangerously close to colliding at Gold Coast Airport on July 21.

The AirAsia plane was taking off from the airport at 11.42am and the Jetstar plane was descending when the two aircraft came within 152 metres of each other.

The AirAsia Airbus A330 was bound for Auckland, and the Jetstar Airbus A320 was arriving from Victoria's Avalon Airport, near Geelong.

The near-miss caused alarms to sound in the cockpits of both planes, although it is unlikely the passengers would have noticed.