The most common thing that businesses leave off their websites (or hide so deep as to be effectively left off) is their address and phone number. Go take a look and you’ll see what I mean. It’s like telling customers “go away, we don’t want to talk to you!”
For airlines, especially smaller ones with a limited market, the most frequently left out important information is “here’s where where why fly.”
America West on the other hand makes it pretty well impossible to find out where they fly. There is a route map available, but to find it you have to look under About AWA / Company Profile / Route Map. Yes, of course, that’s just where you thought it would be.