Spirit Airline is also a cheap airline that offers specials of $1,$2 etc. I have a cousin who just went round trip, with wife and 2 kids, DC to Fort Lauderdale for under $150.00
It is "NoFrills". You are allowed one carry-on plus purse, backpack. If you check lugguage it is $10 a bag, maybe a little less if it is done ahead of time on line. Any snack or drink will cost you, regular airport prices. Most of Spirit's planes are new Airbus A319 and A321's and the seats are ample and good amount of leg room.
Spirit Airlines