How to Save on Air Travel Expenses

This article originally appeared on LearnVest.com.

Airports are notorious for overcharging customers for everything—30 percent markups on food, overpriced duty-free shops, and sky-high currency exchange fees, to name a few. Don’t be that traveler. Here’s how to save before you head out of town.

The free GateGuru app gives users a detailed map of their airport terminal or concourse, along with lots of information about amenities (including Yelp-style reviews). Users can search for specific things ("Au Bon Pain," "A.T.M.") or amenities in a certain area ("Gate B16"). Knowing what's around will prevent you from overpaying for the first option you see.

Many airlines and even some small airports now offer free Wi-Fi, which can save you more than $10 per trip. If you're a frequent traveler, we recommend you download the Wi-Fi locator app "Spots" for $1.99. It works offline, which is key when we're trying to find wireless in the first place.

Many airlines will try to sneak upgrades into your existing reservation. Although paying $40 extra for a premium seat may not seem like a bad deal, it quickly adds up. Instead, check out SeatGuru to identify the best seats you can snag without paying extra.

It’s pretty much impossible to bring water past security, but paying $3 for a bottle of water at the gate is just plain silly. Instead, grab an environmentally-friendly lightweight aluminum water bottle, many of which cost under $10. Once you're past security, fill your own bottle at the water fountain. You'd make back the cost of the water bottle, and earn a profit, by the end of two round-trip flights.

We know that it's a pain to pack a sandwich in addition to packing your luggage, but bringing your own food will really will be cheaper and healthier. Often, even our favorite restaurant chains offer higher prices, and limited menus, in airports. Consider: An entree in an airport restaurant can easily cost $13, whereas a homemade turkey breast sandwich is about $2. Do that even four times per year, and you've saved $44.

While it’s easy to grab a bestseller off an airport bookshelf, planning ahead will save you cash and provide more choice. Buying from Amazon or even a used bookstore can easily put quality books in your hands for around $5, whereas the same mass-market books are sold at airport bookstores for close to $20.

Airport parking and taxis can add up. Plan time to take public transportation—available at most U.S. airports—and save significantly. For example, a cab from New York's John F. Kennedy International Airport to Manhattan costs $45, plus toll and tip. Meanwhile, taking the train only costs $7.25.

Take flights during the early morning, late night, or on Wednesdays, Tuesdays, or Saturdays. Decreased traffic means less chance of a delay, which equals less money spent at the airport shops.

Duty-free shops provide tax-free shopping for customers traveling internationally, but the "deals" are often not worthwhile. Rather than making an impulse buy, take the time to compare prices later, on your computer.

With so many airlines charging for extra luggage, pack everything in a carry-on unless you want to pay an extra $15 to $50. Additionally, if your checked bag is heavier than it's supposed to be, you’ll be charged for the extra weight.

If you’re traveling on an overfilled flight (and you’re on a flexible schedule), volunteer to give up your seat at the check-in counter. If you’re picked, the airline will give you a voucher for a free round-trip domestic ticket, or a $300 airline credit. Customers have been known to receive even bigger rewards when the airline is desperate for spare seats; we were once on a flight in which travelers received $500 and a free hotel stay for relinquishing their tickets.