An investigation is under way into how two planes came within 150 metres of each other in the air at the Gold Coast earlier this month.

The Australian Transport Safety Bureau (ATSB) has launched an investigation into the July 21 incident, which involved an AirAsia plane and a Jetstar plane.

It is understood the AirAsia plane was taking off from Gold Coast Airport at 11.42am as the Jetstar plane was landing, and pilots took corrective action following alarms sounding in the cockpit of both planes.

The AirAsia Airbus A330 was destined for Auckland, New Zealand while the Jetstar Airbus A320 was arriving from Geelong.

The Jetstar pilots were forced to put their aircraft into a climb to re-establish a safe distance between the two planes, after receiving clearance to descend.

“During descent the aircraft warning system alerted our pilots to another aircraft approaching our approved flight path,” Jetstar said in a statement.

“Our pilots took corrective action to restore the safe distance between the two aircraft.

The Jetstar aircraft had to ascend to increase the distance between the two planes. Photo: Getty

“The flight continued onto the Gold Coast and landed without further incident.”

“Our crew did a fantastic job and responded to the situation as they are trained to do. At all times they followed the instructions of air traffic control.”

The ATSB active investigation confirmed the two aircrafts flightpaths resulted in a “loss of separation.”

“Both aircraft received a traffic collision avoidance system (TCAS) resolution advisory … with the crew of the A320 conducting a climb to increase separation.”

The investigation is expected to be completed by July next year.