TWO passenger planes with 443 people on board were involved in a near miss over Mildura's outskirts last year after an air traffic controller failed to notice they were on a collision course, it emerged yesterday.

One of the planes was a Qantas 737 with 143 passengers and seven crew aboard, flying from Sydney to Adelaide, the other an Emirates Boeing 777 carrying 276 passengers and 17 crew, flying from Melbourne to Singapore on September 3 last year.

An air traffic controller cleared both planes to cruise at 30,000 feet, but their flight paths meant they would cross in the same piece of sky 60 kilometres south-east of Mildura in Victoria.

The drama began when the collision course went undetected for more than 17 minutes, according to an Australian Transport Safety Bureau investigation. A "conflict alert" flashed up on the air traffic controller's radar screen, the planes less than 19 kilometres apart and closing fast. As the seconds ticked away, the air traffic controller tried to make contact with the Emirates pilots three times, to no avail.

A minute after the alert, the gap had halved to 9.1 kilometres - breaching the allowable minimum space between the aircraft - and he radioed the Qantas pilots to "turn right", which they did.