This is the correct answer. It has nothing to do with fuel prices. Oil has been stable for years, and all airlines hedge out their fuel costs years in advance.
What happeneed is that many airlines consolidated, meaning reduced flights, less seats, and better pricing power. Flights are averaging 90% full now compared to less than 70% 5+ years ago. Also, airlines are getting smart charging for everything - food is ala carte, bags are extra, exit rows are extra, everything adds to the bottom line.
Airlines are no longer really hedging this. Southwest was the money maker a few years ago because they got lucky and hedged on the upward price swing, but since it's been stable, it's been a losing prop.
I'm pretty sure US Air dropped their hedges after the AA merger