It is perfectly legal (assuming an open drivers licence) to drive to work when your blood alcohol reading may be .03 however if randomly tested once at work, could be dismissed for having any alcohol reading at all.
This naturally excludes those occupations with a zero tolerance for alcohol.
Given that at Melbourne Airport definately and most likely other airports the there is a zero alcohol policy for operating equipment on the airport. This is not a Qantas policy but an airport operator one which Qantas must comply with.
Starting to see why this stuff is happening?