Last Thursday a Qantas Cityflyer 767 and a Tiger Airways A320 carrying a total of about 432 seats came within 3.8 nautical miles of each other while flying in opposite directions  through controlled airspace over Tamworth. The Qantas Boeing had been assigned a southbound track at 36,000 feet flying from Brisbane to Sydney while the Tiger Airbus had been assigned the same altitude flying northbound on a flight to Brisbane.

In a brief summary of its continuing investigation the ATSB  says AirServices Australia instructed the Qantas crew to climb to 37,000 feet, and says “there was a breakdown in separation standards as separation reduced to 3.8 nautical miles and 800 feet”.

Crikey understands air traffic control did not act on the conflicting flight paths, which intersected over Tamworth, until they were 23.7 nautical miles apart, with each jet travelling toward a potential collision at a speed likely to be well above 400 knots. The risk of a disaster was averted by Qantas climbing over the incoming Tiger.

But the incident was placed in the lowest ranking category of ATSB investigations on its website this morning, in a cluster of notifications with the same date.

This is a closer call between two scheduled airlines than the officially serious incident over Launceston between a Virgin Blue 737 and a Jetstar A320 in  fog in uncontrolled airspace on May 1, 2008,  that was the subject of an ATSB final report last week. In this case the two airliners involved aborted their closely scheduled first approaches to the Tasmanian airport because of low fog and then ended up on conflicting paths because the Virgin Blue crew “did not adequately communicate their intentions” to the Jetstar pilots.

That report, which put the minimum distance between each jet at around 2.6 nautical miles, was accorded the highest level of inquiry by the ATSB while last Thursday’s incident is consigned to an importance normally given to light aircraft incidents. After raising this seeming anomaly this morning with the ATSB the air safety investigator said the Tamworth incident involving Qantas and Tiger could be upgraded.

Which of course raises the question, how could such an apparently dangerous situation involving two jet airliners under the control of AirServices Australia not come under such scrutiny at the outset. The normal procedure at the ATSB is to downgrade investigations involving high capacity airliners in Australian airspace if initial inquiries merit this, rather than the other way around.