I find it somewhere between amusing and perplexing that likes of Gottliebsen doesn't seem to grasp the very basic concept of "Revenue received in advance".
All airlines typically receive payments for flights in advance of when they actually operate the flight. Very often, the receipt is well in advance of the actual flight.
The money received goes into revenue. The equivalent value is then held on the balance sheet as a Liability. It is not held as an asset and it is therefore not "capital". The whole thing is a simple and basic business practice with well established accounting rules.
What is often instructive is the ratio between total passenger revenue received by an airline and "Revenue received in advance". For Qantas the ratio is about 29 percent. This is not, by any means, unusual.
For comparison, Southwest sees an "air traffic liability" (one of the US terms for "Revenue received in advance") to total passenger revenue ratio of around 26 percent. Singapore Airlines runs a similar "Sales in advance of carriage" ratio of 26 percent. Delta, United and American Airlines typically see lower ratios; often somewhere in the teens.
Virgin Australia currently has a ratio approaching 40 percent. I'm yet to see much hand wringing about that.
Virgin also holds $290 million of unredeemed Future Flight credits that are currently due to expire by 31 December 2023. When that liability is written down to zero that will be the equivalent of Virgin converting passenger revenue paid in advance into capital. And I'm yet to see much hand wringing about that either.
And Virgin has assets of just over $3.7 billion and liabilities of a shade over $5 billion for a balance sheet that is underwater to the tune of $1.3 billion (a shade over $1 billion come the New Year thanks to those written down flight credits, or "theft" as it is known in some circles).