Flyertalk has some ads about Frontier's winter sale for travel before 3/7/2012. Seems like a transcontinental domestic flight can be had for $99 (actually $120 after all the fees). That is about $100 less than other airlines. I bought one for 2 months from now.

Thanks for the advice. I think F9 will be around in 2 months. It seems that I might not get useful miles for this. I have a F9 Early Returns account but I haven't flown on F9 for 6 years. I can't find any other airlines which credits Frontier flights.