If you’ve ever shopped for airline tickets or stepped aboard an airplane, this Q&A is for you.

It might even save you a few bucks on your next trip.

1.) Which airline has the cheapest flights? Any one of them; it just depends. Ticket prices vary based on when you buy, when you fly, even how you fly (such as non-stop vs. connecting flight).

While the so-called ultra-discount carriers often have very good deals, even they won’t always have the best fares. Example: A recent check of cheap flights in May for round-trip flights between New York and Fort Lauderdale showed a Spirit ticket for $161, while a United fare cost only $148.

Bottom line: Shop for tickets on an airfare comparison site or you might pay too much. Sometimes your favorite airline will have the best deal, but not always.

2.) Planes cannot leave until the precise departure time, correct? Planes can and do leave early, though such departures are rarely more than a few minutes before the official departure time stated on your ticket.

Sometimes this can happen because the boarding process went unexpectedly smoothly, or maybe a mechanical problem got fixed a lot faster than anticipated. As Delta states on its website, “Flight schedules are not guaranteed,” and I’ve heard several anecdotes about different airlines where planes took off before a straggler or two got to the gate.

Bottom line: Don’t be late. Many airlines provide guidance for getting to the airport. For example, American suggests anyone traveling within the U.S. arrive 90 minutes before departure.

Related: Love Your Coffee? Think Twice About Drinking It on Airplanes

3.) Fliers never pay for carry-on bags, right? Unfortunately, that’s not the case.

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Discount airlines like Allegiant, Frontier and Spirit charge for all bags, and discount transatlantic carriers like Wow Air do the same. There are other restrictions too; for instance, carry-ons aren’t allowed in American’s Basic Economy class at all. They must be checked for a fee.

Bottom line: Check all fees before you ding your credit card to get the true total for your ticket.

Check all fees before you ding your credit card to get the true total for your ticket.

4.) Are some days more expensive to fly than others? Usually, yes. Flights within the U.S. are typically most expensive on Fridays and Sundays, and this is largely because these are the most popular days to fly. Better deals are usually available on Tuesday, Wednesday and Saturday when people are less inclined to fly. For international flights, weekends are usually more expensive than weekdays.

Bottom line: A deal-finding tool can pinpoint the cheapest days to fly within a month or season. Can’t fly cheap days in both directions? Fly one cheap day and you’ll still save something.

Related: Flight Went Wrong? Here’s How to Make Things Right

5.) Whatever happened to my old favorite, U.S. Airways? Or AirTran? U.S. Airways flew its last flight in 2015 before the name vanished into a merger with American; AirTran disappeared the year before into Southwest.

And if you’re wondering what’s happened to Virgin America, its brand disappeared just a few days ago, on April 25, in the merger with Alaska.

This Fox News piece is used by permission. Rick Seaney is an airline travel expert and the co-founder of FareCompare.com, an airfare comparison shopping site.

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