Q. I recently flew from Atlanta to Chicago. According to the airline site which I checked before booking, one checked bag should have only cost $25. However when I checked my bag at the airport, I had to pay $30 for my one checked bag. Why the difference?

A. Some airlines will offer a slight discount on checked baggage if you purchase before your flight as opposed to waiting to pay at the airport during check-in. This practice is more common among low cost carriers such as Frontier or Spirit.