I think it's not a margins issue - plenty of good money making machines doing this - but definitely a not-enough-competition issue.

There is competition and they're all the same. It's a capitalism issue. Less expenses = more profits and that's literally the only thing that matters.

Corporations only do things for one of two reasons - money or regulation. If they don't have to and it doesn't make money, they don't do it.

Nope, there used to be a lot more airlines, all now absorbed or merged to a few select ones. It’s not a profit issue, but their ability to survive.

what is your alternative system to capitalism?

Never claimed I had one. I just don't think the current system works very well.

CEOs are overpaid and have too little liability. Corporations happily break the law and in many cases the only consequence is that they have to pay what they should have paid in the first place. Or a slap on the wrist fine that's less than they earned from the crimes.

Get rid of corruption and enforce laws properly would be a good start.

Capitalism is just a system where industry is own by private entities and is for-profit. Corruption or laws have nothing per se to do with capitalism.