Haven't listened to the analysts comments yet, but the reason for the stock to continue dropping is around the 11:30 mark.

Spirit, as the call has stated has been an airline looking for margins in the high teens, with the margins of 26.9% reported this quarter, the guidance for the future is back to the high teens. That coupled with decreasing RASM and decreasing revenue guidance, with ticket prices declining, it's only natural that the stock will drop. I think Spirit is pretty conservative in its guidance, so I can see future margins around 19-22% just as a guess.