[ryan-c]

Southwest (I fly with them a lot) isn't a "budget" airline in the sense that Allegiant or Spirit are.

They don't do assigned seating at all - you pick an available seat when you board. Boarding position is generally assigned based on when you check in, though you can pay extra to board earlier. They include two checked bags per person and standard carry-on allowances in the price of the ticket. No "gotcha" fees.

One similarity is that there are a lot of larger airports that they don't service, instead using other nearby airports.

They're inexpensive if you book well in advance, but last minute fares can be very expensive.