When you buy the cheapest seat, it’ll be no surprise to find yourself in the middle of a three-across row. And seat mates could too often be a 300-pounder and/or ever-wailing baby. And, of course, the more popular the flight, such as Thanksgiving and Christmas weeks, the higher the ticket price.

So, when can you do the biblical plea and get a blessedly upgraded seat at no extra cost? First is scheduling your flight when there are more chances of unsold seats. They include non-holiday weekdays, early morning and late night (redeye). After you’re aboard, all passengers seated and doors shut, note all empty better-positioned, more comfy seats.

Then, politely ask a flight attendant to move you to a premium seat for free. It may not work every time, but it’s always worth the effort. And now that some airlines are encouraging tips to their employees, offer some dollars to improve your chances of flying in upgraded comfort.