Legacy designation has nothing to do with number of routes an airline flies (Southwest is not a legacy carrier) but is determined by quality of service available specifically first class and business class and other in-flight service. This is where you split and have the "low-cost option." This legacy service can also extend beyond just the aircraft and into the area of lounges, frequent flyer programs and airline alliances and the alliances are a key ingredient in Hawaiian Air and Alaska Air. Legacy carriers also have world wide operations but that is a rather obscure term since those operations are the result of various alliances. The traditional "big five" (Big Four, really)are legacy carriers and the other two are also part of the mix. Maybe classifying them as a sub group is more appropriate? I won't even touch on the deregulation in 1978.

The DOT has a breakdown of how reporting flight delays take place. There are so many holes in this reporting process that I could fly an AirBus 380 through it and UAL has done just that. Just think of any airline that uses Newark extensively and you are already dead on the reporting.