• Airlines charge varying prices for the same seat depending on which version of their website you view.

• By searching for flights in foreign currencies, you can potentially find a much cheaper price.

• Be sure to use a credit card that waives foreign transaction fees when you do this.

Read Insider's guide to the best travel rewards credit cards »

You've probably heard people swear by spurious tactics for finding cheap airfare — things like "always buy on Tuesday," or "perform your search while incognito."

Those techniques are garbage. But one even more bizarre method does work. And almost nobody knows about it.

For whatever reason, airlines sometimes list seats at vastly different prices based on which version of their websites you visit. For example, if you search for a ticket to Paris through the Air France website, the price difference between the US site and the French site could be hundreds of dollars.

I've used this trick many times to save a ton of money in the past. I'll show you how to do it.

Book cheaper airfare by using a different version of the airline's website

Unless you've made a concerted effort to avoid it, the airline website knows which country you're searching from. It will default to that country's currency — and the unique prices it charges for that particular market. The difference can be staggering.

Let's look at an example.

When searching on Japanese airline ANA's website, you'll see that a round-trip flight between Chicago (ORD) and Tokyo (HND) this summer costs $2,811.95.

However, by simply switching to the Japanese version of the website, the same flights cost 219,110 yen. That amounts to about $1,580 at the time of writing.

Additionally, the Japanese site reveals discount fare classes that don't show up on the US site. The US site offers "Flex Special" Economy, "Flex Special" Premium Economy, and "Flex Special Plus" Premium Economy. But the Japanese site includes an extra-low rate: "Super value" Economy.

Obviously, it's not always a win to book in foreign currency. Sometimes booking with USD is the cheapest option. In another example I tried, a flight between New York and Paris costs $442 with Air France. Booking the same flight via the Air France website costs 1,047 euros — which equals $1,128 at the time of writing.

To search prices from other countries, you shouldn't have trouble finding an icon that allows you to toggle your location (it's often at the top right of the home page). It may take the form of:

• A flag of the country you're searching from

• An abbreviation of the country you're in

• A currency symbol

When you change the country to something other than the US, the language may also change. If there is no English option, a web page translator extension can make your booking process much easier.

Be sure to use a card that waives foreign transaction fees

When you use a debit or credit card to make a purchase that is processed outside of the US, you could be charged foreign transaction fees.

In other words, even if you buy your airfare at home, you might be subject to a fee if you're paying a foreign airline. Most credit cards will charge somewhere around 3%. That can add up quickly — especially when you're paying for airfare, which can cost $1,000+ depending on where you're going. A small family could find themselves paying well over $100 in foreign transaction fees alone.

That's why it's important to use a credit card with no foreign transaction fees.

Most of the best travel rewards credit cards don't tack on these pesky fees. There are even a handful of no-annual-fee travel credit cards that waive foreign transaction fees.

These cards also come with benefits like travel insurance, travel-related statement credits, and valuable rewards for your everyday spending. Even if you travel just once or twice per year, you should have at least one travel rewards credit card.