The Australian authorities are investigating after a Singapore Airlines (SIA) plane and a Jetstar Airways aircraft came too close as they flew over northern Australia on Thursday.
The SIA jet was cruising from Brisbane, Australia, to Singapore when a Jetstar aircraft from the opposite direction started to climb and the planes got too near each other.
It is not clear what the distance between the planes was or if there was any danger of a mid-air collision, but it was serious enough to warrant an official investigation by the Australian Air Transport Safety Bureau.
A bureau spokesman told The Straits Times yesterday: "We get about 100 such cases a year and investigate a small number that are deemed as potentially more serious. This does not necessarily mean, though, that in this case, there was any danger of a mid-air collision."
The Jetstar flight from Darwin to Brisbane was acting on air traffic control instructions when the incident happened early on Thursday near the town of Katherine in Australia's Northern Territory.
The Straits Times understands that the pilots were alerted by the aircraft alert and collision avoidance system, which sounds a warning when planes go too close.
Aircraft must typically keep a vertical distance of between 1,000 feet and 2,000 feet, with the exact distance depending on factors such as how high the planes are and in which air space.
Captain Ajmer Singh, chairman of the SilkAir branch of the Air Line Pilots Association - Singapore, said the system not only alerts but also instructs pilots to take the necessary action.
He said: "The alert system in one aircraft is constantly communicating with other planes in the vicinity. If there is a breach in minimum separation rules - either vertical or horizontal - there is an audio alert that goes 'traffic, traffic'.
"The system will then instruct the pilots to ascend, descend or take other corrective action."
SQ246, an Airbus 330 which left Brisbane at 11.30pm on Wednesday with 177 passengers and 14 crew members, landed at Changi Airport ahead of schedule at 5.20am on Thursday, said SIA spokesman Nicholas Ionides.
He was unable to provide further details of the incident as it is being investigated.
The Jetstar aircraft, Flight JQ673, was a smaller Airbus single-aisle A-320 jet.
As the skies become more crowded, aviation analysts have stressed the importance of technology and well-trained personnel to ensure safe skies.