If you've ever flown on a budget like this couple, you know that you've got to pack as light as possible. Some airlines will let you fly for a double-digit price, and you think to yourself, “What a fantastic deal!” Sure, you may have long layovers or have to fly at 3AM, but you're saving so much money! But once you read the fine print, you may realize that you're stuck. That airline is only going to let you bring a bag and a personal item, and they're going to be very strict about the measureme…