Agree with everyone here 100%.

Because of my travel style (I'm a young, single college student--i.e. flexible--with a moderately low budget), I love Kayak's Buzz feature, Travelocity's Flexible Dates option, and Travelocity's Dream Maps option. Anything that helps me find when and where the cheap fares are is welcome.

Kayak's Buzz option is really the best interface, but the downside with it is that because it's based only on searches that real users have actually done and is not integrated with the actual publishings of fares, it's not comprehensive. FareCompare's Destinations option is extremely promising, but it suffers from the same problem that Travelocity's Flexible Dates does: it initially only searches by the published dates, not by availability, so it takes awhile to find a valid set of dates on which the fares are actually available. I understand that this is because the GDS systems charge fees for every actual seat lookup. This should not be a problem on an airline's own site, as they do not need to pay a GDS system since they are looking up seats on their own system.

A combination of Kayak's Buzz, Travelocity's Flexible Dates, and (of course) booking directly with the airline to avoid the GDS surcharges is what allowed me to fly ANC-BOS/LGA-ANC for $380 on United. That's extremely good for flights from up here (often ANC-SEA is >$400 rt).

If United really wanted to secure my business, they should have let me find all of that out at united.com.

Of course, as someone else mentioned, it's time for the legacy carriers to dump most of their fare buckets and go to a simpler setup like Southwest does. People go to southwest.com because they know (regardless of the interface options there) that they can get a reasonably-priced ticket with a minimum of confusion and hassle. Things like fares and the like are pretty much out of your control as a web designer, but that's something to pass on to management--that people are driven away by the difficulty of reliably finding good fares. (I NEVER just go to www.alaskaair.com, put in a pair of dates, and search for ANC-LAX. Doing that always brings up something in the $600-800 range. I've never flown to LAX for more than $450, and often I'll do it for $250-350. In contrast, it's no problem for me to go to southwest.com and find my grandfather a very reasonable fare from BUR-TUL without a lot of extraneous searching. So, Southwest has his business. (I do typically check a little bit to see if I can beat that price on any other airlines, but Southwest usually has the best fare.)

There should NEVER be a reason to have to call the callcenter (and I'm sure airlines would like to not have to hire as many people), whether it's for itinerary changes, award reservations, or whatever. If the CSR can do it on his or her computer, we should be able to do it on our computers. This includes searching for partner award availability. I became an Aeroplan member just so I could use Air Canada's web site to find all Star Alliance awards. If they can do that, why can't other Star Alliance sites? With United, I have to call them to see if any of their partners can fly me to a destination. And with United's awards booking engine, I have to search specific date pairs (although they do search a few days around those dates, which helps a little). But if I call them, the agent can search months of availability with just a couple of keystrokes. Why involve her? Why not let me do it at home? Perhaps the airlines don't want us to know that much about their availability, so they hide it behind a CSR. But it would really save costs and hassle and make me happier with them if they allowed me to just do it all online.

AA.com offers an option to search all carriers, but it never seems to work. I can't say that it's fair to request that an airline direct business to their competitors. Having said that, it would be a really nice feature...

Definitely remember my dates and airport pairs when returning to the search screen to modify something. That's a no-brainer (and REALLY annoying!)

Agree with the popup calendars. Let me type it in manually if I want. If I need a calendar, make a little calendar button that I can click.

There are lots more that I can't think of now--I'll start making a list next time I search for a flight and post my results.