I saw this fascinating graphic over on USA Today's website last week and had to post it here. Below, you'll see a color-coded map showing the year-over-year change in number of airline seats by state. This is using projected October 2008 schedules versus October 2007, so it's likely this will get worse as the airlines crystallize their Fall schedules.
I highly recommend clicking on it (it will take you to USA Today), because it's interactive. It will break it down within each state so that you can see individual airport changes as well.
On the other side, you'll probably be surprised to see Wyoming have such a large jump. The entire state has 1,679 seats per day. To put that in context, that's about the same number as Branson/Springfield, Missouri. So that's not really a big deal, to say the least. In fact, it's relatively meaningless.
In general, it's mostly negative numbers across the board. Any exceptions? Sure. San Francisco is hanging in there. That's probably a direct result of Southwest's growth along with Virgin America's birth. And Denver is up as well. A thank you is due to Southwest for that one too.
Overall, you can see that capacity is down significantly and it will only continue to drop. Fares will go higher, but the silver lining is that fewer planes mean fewer delays.