80% would be way too much, the consumers would catch on and probably not buy tickets anymore. But don't worry, the airlines' best MBAs will be hard at work calculating the exact percentage of flights they have to fly before it starts hurting the bottom line. And once all airlines start doing it, they could bring that percentage down - what are the consumers gonna do if that's the only way to get to the destination?

Exactly. These supposed benefits of deregulated markets dissolve when the sellers have pricing power.