Smart travelers have discovered an unspoken disparity in airfares on international flights.

Because of different fare categories and foreign exchange rates (such as the power of the U.S. Dollar versus the Euro), it often makes a big difference in which country you make your reservation.

A flight from Los Angeles to Sydney was recently priced at $1637 round trip. This ticket was purchased on a website in the U.S., using a U.S. address.

But the same flight bought using an Australian address—and paying in Australian currency—was $804.

These discrepancies can often save you a lot of money, so make sure to do your homework.

When signing on to the website of an airline not based in the U.S., pick a different country of origin —often the currency of the home base of the airline itself.

This kind of cross-border ticketing can seem confusing, but the savings can be substantial.

But remember, when you get your credit card statement it will be converted to U.S. Dollars.

For more information about booking online and foreign currency, check out:

• Booking Online? Watch Out For These Airline & Hotel Travel Scams
• Tricks for Getting Better Exchange Rates
• Travel Apps That Help You Take the Guesswork Out of Travel

Keep reading for more travel tips.