I worked for Frontier for a smidge.... depending on your departure airport, some of the gate agents are very shady, they get $$$$ for every bag they "flag" at the gate. Charges around $90 bucks! I've seen people throw away personal items, shoes, clothing anything to get the bag to 40 pounds, and other people take wheels off bags to make them fit. Also, if you dare speak to a ticket agent, they'll charge you!!! Be prepared. Oh the stories... Shady, shady, shady...