Fares from Miami to major work destinations such as Chicago in my case have to be purchased 6 to 8 weeks in advance to get the cheapest fares.

American does have more flights than anyone out of Miami but I use United as the service is ten times better and they were also the only carrier to use 777's on my route so it was a no brainer.

And Miami, as Rudi pointed out is probably the only RCC in the USA to offer complimentary Liqour and beer which is very nice when I travel on vacation. Don't mind being early for the plane one little bit!