One thing I used to do (forgot about this) when I was less interested in getting there quickly, and more interested in piling up segments and frequent flier miles was use Continental as my primary airline (from Dallas). Once you reach top tier in their frequent flier program, getting free upgrades to first class is nice.
If I wanted to get somewhere quickly I used American, but if I wanted to pile up miles and upgrade to first class I used Continental. I can’t say if Continental still has this policy but American always charged miles for upgrading.
