system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are the airlines complaining about profits when so many flights are so full?

Utterly anecdotal but I can't remember the last time I was on a flight with more than a handful of empty seats. Even the super-early and red-eye flights I've been on have been near full. 

Am I just super unlucky and 90% of flights are nearly empty, or are they just incredibly bad at running their businesses?
gpt
You're looking at the wrong thing.

Don't look at seats on a plane, look at financial statements.  These companies are barely able to keep their heads above water because they are so cutthroat competitive with each other, so their margins are razor thin.

And their greatest expense is also the most volatile - fuel. 

In the end, for every $100 you spend on a ticket they might see a dollar or less in actual profit after all of their expenses are covered.  A single disaster of any kind, even just a small increase in oil prices is absolutely brutal for these companies.