A "contract" is one thing, but under Fair Trading legislation what you offer the customer either implied in advertising or represent in a way that a reasonable person would expect it, then that is what you sold. Proving what is what is another matter, but in general it comes down to how the "product" was represented.
I work in Telco, so fair trading is something that they hammer in because the ACCC takes such an interest in it. Advertising things like "unlimited data" gets smacked down because in reality the fine print says you get throttled or have excess charges, which is not really "unlimited". Other far more subtle issues come up with the way products are advertised versus how the contract plays out - even things like wording such as "premium" or "discount" if they imply something the contract does not deliver or does not deliver as you expect. There is also laws about bait advertising etc.
In my view, if you go to Qantas to buy a ticket from A to B, you do it because their advertising shows you the nice planes and the smiling hosties and people relaxing in a happy cabin. It is a "premium" product even if you are flying economy, versus the "cheap fare" product they also offer. As you bought the premium product, that is what you expect. If you don't get that as a reasonable customer, regardless of the reason, they are obliged to make up for it i.e partial refund or some other offering.
Most reasonable people would understand a flight being delayed or a maintenance isssue, and might just be happy to get to their destination, so no real issue. Still, I think it would be at least good customer service to do something to make up for the shortfall between a cheap and premium service.
Now, if they are selling seats knowing full well they are going to bump people to a cheap alternative, then that could be viewed as bait advertising (big smacks) - good luck proving it though.
I don't think any of this would apply to something like JitConnict because its more of a subsidiary service at the same level, rather than a separate product they are trying to shift you onto.