I am a major OCD freak about babysitting my reservation. Once years ago I noticed on American Airlines that my First Class award ticket switched from an Embraer without First Class to a MD 80 with First Class on a SFO/Hawaii/SFO flight and this was on the short LAX-SFO flight. I called up American and they put me in First Class. They did not automatically upgrade me.

I saw that my seat has changed so I called up the airlines and got an even better seat than the one I got before. The airline is not going to call up everyone who has been reassigned. I look at my reservations twice a week for schedule changes etc.

Once an airline completely obliterated my itinerary and I was on the phone in a New York minute and got an even better itinerary that would have costed more with a better schedule.

Last year on Delta I booked my Father and I in Comfort+ from San Jose CA-Vancouver-San Jose via Seattle and my Mother had regular Economy. One day I went online to see her itinerary and got Comfort+ for $10 more than she paid. It could have been a pricing mistake but who was I to turn it down. Not only did I get her Comfort+ I got her a seat behind my Father. It was the best $10 I spent.

My point is its the passenger's responsibility to look at their reservation every so often and call up when you see something amiss.