I am probably not going to be too much help, but I know when we flew Midwest in September we just paid for the baggage at the airport. It was actually really easy. The only word of caution was we flew out of MKE and when you get there you pay for it via kiosk and they do not accept cash only debit/credit card. So be prepared. I did check in online and do not recall the option of paying for luggage at that time, but I could very well be wrong also. I hope this helps a little.