> All of the fat in the industry has been squeezed out
I don't know where you live but in the US this is patently not true.
Airlines are an abusive oligopoly there, with landing slots and the like cementing control of certain markets for certain airlines.
Ticket prices are much higher than they used to be and are much higher than Europe (for instance).
Airfare in the US costs less today than it did in the 90s, adjusted for inflation: https://www.bts.gov/newsroom/2024-annual-average-domestic-ai...
Plane tickets in the US are, inflation adjusted, historically low. Further, the airlines themselves seem to be on perpetual life support and have variously gone into bankruptcy and resuscitated.
You see an oligopoly, but the barrier to entry is as much defined by the thin margins and high capital cost as anything else.
Airlines have substantial earnings (greater than flying?) from credit card marketing and loyalty programs.
The airline industry is famously unprofitable; it is commonly said that on net, the sum total of airlines have made $0 over the course of their history. It is true that there are periods where they do make a profit, but these periods are offset by times when they make massive losses (such as during COVID, after the Great Recession, and after 9/11).