AirTran, Southwest, Midwest, etc. Seat Assignments

[traces7]

On most airlines do you get to choose your seats when you buy them? I know that on AirTran and Southwest you get your seat assignments when you check in right? What about Midwest?
Thanks

 

[DebbieB]

With most web fares on Air Tran you can get your seat assignment 24 hours before with online check-in.

Southwest does not assign seats, you get an A, B or C boarding pass when you check-in, either online or at the airport. Then everyone lines up and boards by A first,then B, then C, choosing a seat once on the plane.

Don't know about Midwest.