At first blush, it seems like the airline sector is in a bit of a golden age at the moment. The sector has consolidated to the point where most of the carriers can earn a decent return on capital. Gates at the airports are locked up making it very difficult for new entrants to get in the jet travel business. This makes it easier for the big guys to nickel and dime you for luggage and onboard snacks. But, the industry is a mature one and revenue growth in passenger miles has slowed to a crawl.