But even though payment has not yet been finalized, you HAVE engaged in a contract with this airline. If airlines start cancelling flights maliciously, they'll be in a lot of trouble.

And even if they're not malicious. A bus company in my country got fined (or, denied millions in subsidies) because they didn't meet their target of bus routes / bus lines (they get subsidies to drive routes that don't pay for themselves). They couldn't get enough bus drivers due to the Panny-D and everything else going on.