Spirit Airlines passenger, Brian Svigel, stuffs his bag into a template to check to see if it classifies as a 'free' carry-on or if he has to pay $40 before Spirit Airlines first outbound flight to Las Vegas at gate A31 at Denver International Airport Thu [Getty Images]

Spirit Airlines passenger, Brian Svigel, stuffs his bag into a template to check to see if it classifies as a 'free' carry-on or if he has to pay $40 before Spirit Airlines first outbound flight to Las Vegas at gate A31 at Denver International Airport Thursday morning. The bag did not fit and Svigel had to pay the fee. Andy Cross, The Denver Post (Photo By Andy Cross/The Denver Post via Getty Images)