Sure, but those kinds of structural issues are the airline's problem. BA's pilots are underpaid if they are so in demand, and BA would have to pay a lot more to poach pilots from other airlines.

If they're underpaid, sure. (And I would assume they are) But that was the original question - what are the working conditions? If they were paid $1M a day (of course they're not), would you still say they're underpaid just because they're in demand? What about $300k a year? What about $200k?

This article doesn't say what the pay / demand is. Another one (https://www.theguardian.com/business/2019/sep/08/ba-pilots-t...) mentions BA proposing an increase that would bring "some" over £200k a year. I'm sure that's cherry-picked for PR and doesn't show the whole distribution, but it's at least one number.

If they were paid $1M and could get more then they are still underpaid and there is sufficient demand.

There is no absolute number at which they are no longer underpaid, it is completely relative to how much demand there is and how much companies are willing to pay for that demand.

If the airlines and pilots existed in isolation then maybe. If they were paid 1M, I'd think they're overpaid and the tickets should be cheaper instead. There definitely is a threshold compared to all other salaries / cost of living / economy where the pay would become irrational - regardless of demand.