I would like to provide an apposite advice. Visit the Delta, BA, AA, and United sites. Create an account, log in, try to do stuff. Those sites stink, but each in its own way.

Then create user scenarios around all the things people are talking about and see if you can find some commonality. Especially when you try executing on the competitive sites.

For instance, much talk of route maps. I would love to be able to work in a pure map view when I do a multi-hop multi-carrier trip. Can't make Paris work, well, then I can see that Orly isn't that far off... Others want route maps to show or hide partners. So steal the map control button concept from Yahoo.

Thanks for asking!