From the Australian article:
"...but Perth Airport chief executive Brad Geatches said his organisation was insisting that Air Australia pay outstanding charges. "We're not aware where others might be on the subject but we will be quite insistent on receiving payment," Mr Geatches said. "We are sensitive to these matters; I've got two Ozjet aircraft sitting on my airfield that are a constant reminder to our company of the risk associated with airlines failing."
This is exactly what was happening to OzJet at the end of their life cycle. PER wouldn't let them fly until they paid their bills. I believe it was about $200k that they owed.