Why did both crews not throw on 'gas for Mum'?
Maybe the Virgin aircrew did just that. Arrived at Mildura to find Qantas asking for the first go because of low fuel. Virgin agrees because they have "gas for mum"
Virgin hold until Qantas lands and clears the runway and then start their approach.
In the meantime the fog gets thicker and so carrying "gas for mum" has painted them into a corner.
And here we are, with 20/20 hindsight, trying to second guess what two crew did based on information presented to them.
As a matter of interest, how many times in OZ have RPT jet aircraft been forced to land in weather conditions that have been below the minimums or non normal conditions (night, etc) after having used all the flight fuel and their variable fuel.
Before this, I can think of at least 4.