I know people have their preferences but my brother is moving to Austin and will be traveling for work weekly. He could also fly from SAT since he's going to be in the San Marcos area but from what I understand it doesn't offer any better flights and can be expensive. Alot of his clients will be in the Southern Central US (TX,OK,AR,MO,NM) but some might be other places. The way I see it he has 3 options

1. Southwest: Southwest offers nonstops to 10+ cities from Austin and connections close by via DAL and HOU. He would likely earn a companion pass so that would be a nice perk.

2. American: Primarily alot of service via a short hop to DFW. However he might get stuck on RJs Though First Class is a possibility but short flights could make this less attractive.

3. United: Should offer many connections in the area via IAH, same issues apply that AA had.