For those who don't know, at one point there were 6 major airlines in the USA that covered the US from coast to coast. There are only 3 now. Here's who gobbled up who:
Delta bought Northwest Airlines
United bought Continental Airlines
American bought US Airways
Southwest Airlines is a really big small airline because it only cover major US cities.
Of the above, by the time of the various mergers, US Airways was easily the most consumer hostile major US airline. Many of their fares didn't earn miles at all, as I found out to my horror when I booked a flight on them intended to earn miles with a partner airline on the flight. Their whole attitude was basically you can over pay for your ticket if you want miles or you can get nothing. They had a branded credit card and it was horrible, offering the lowest miles accrual rates in the industry. So it made perfect sense that American would buy them as American was easily the 2nd most customer hostile airline in the USA. I can tell you that American does not value their customers at all and if they have a way to squeeze more money out of a customer and make that customer's experience worse, they will do it. United has at times been some incompetent in dealing with customers although I think they do care about them. Delta did value their customers until recently. Now their CEO, much to my surprise, seems to be fully committed to screwing all of them over.
Delta's biggest problem in my opinion was that for many years they made it too easy to earn special status. I'm not exaggerating when I say that every Delta flight has at least half the passengers with some kind of special Delta status. Even I have a special status with Delta, although it is rock bottom dead last of all statuses, through a branded credit card. I read the other day that Delta is testing a new type of screw the customers business class ticket where the default business class ticket won't give you anything unless you want to pay for it. No assigned seating. No checked baggage. Are there really customers who want to pay thousands of dollars for a ticket without assigned seating and no checked bags? Delta seems to think so. Or they simply now want all business customers to pay extra for those. And this demand pricing for sure means that you as a Delta customer will always get the worst price they think they can make you pay if you want to fly with them. I fly United sometimes and in this race to the bottom where Delta and America seem determined to see who can piss off the most customers, I guess going forward I'll just start using United more if they end up staying out of this.