I think part of the Legacy carrier problems are non-airline competitors.
Fractional ownership. The reality is that fractional ownership (i.e NetJets) is the penthouse at the Grand Hyatt. (A personal aircraft would be owning a summer home in France...) The issue here is that the entry price point for NetJets has come down in recent years. Also, the "hassle" factor of the commercial airlines has increased the perceived cost of airline travel to top end travellers. Therefore, fractional ownership doesn't have to be for the extremely elite anymore, just the fairly elite. Furthermore, the larger the market, the more intense the effect, IMO. I.e. NYC will foster many more NetJet users than RDU, for example. This is true because, not only is their a concentration of wealth and power, but the airport/airline system is more difficult to use, and therefore more costly to the elite traveller. So the cost of airline travel to the extremely time sensitive traveler has increased, even though the fares are only at "traditional" levels.
Telecommunications. Video conferencing, et al, reduces the need to travel. While face-to-face communications are still important in business, video or audio conference calling can substitute for some meetings. Even Dave Siegel, CEO of an AIRLINE, has used this when the "cost" of travelling was not as great as the perceived benefit of "being there". These technological advances decrease demand for last-minute high fare travel.
These two items, I believe, are reducing the number of high fare passengers in the airline market. Since the airline pricing model is based on high fare passengers subsidizing low fare passengers, this is an issue which needs to be addressed.