We did a study in a management class at ASU
my senior year in 1997. We took a look at UA
airlines and determined that it was a strong airline, and could maintain its position because of high barriers to entry on its key long haul routes.
The professor disagreed and said he knew for a fact he could lease a second-hand 747 for $300,000 year with a crew. And he said for $1M, he could have an operation up and running within a few months.
I did not believe him. I still don't. As I think that you could even lease a 737 for $300k/year with a crew, right? An internet search on Google taught me as much.
If you had $100M and knew you could get 80% load factors, which are both really hard to obtain (see JetGreen), then I would say your best bet would be a regional airline offering unique, but popular routes. I would go with a fleet of 737's, offering service from Austin, TX
and Pittsburgh, PA. No flight would be longer than 3hrs, and each aircraft would perform at least three R/T's per day. For cabin staff, I would use child labor. Cute kids pushing lemonade would attract more customers!
Keep on truckin'...