1. Fare buckets similar to Southwest's website
2. automatically pulls up the "do you want to upgrade" when you purchase a ticket.
3. automatically pulls up seat assignemtns
4. ability to change seats after booking online
5. ability to find the nearest airport to a city served by that airline. I sometimes use
http://aviationtoolbox.org/old/nearby_airports
but that gives me all General Aviation airports that are not necessarily served by air carriers.
6. ability to sort the outputted matrix of flights by price, connection city, arrival time, departure time