Editorial Note: “Here’s How To Tell If A Cheap Flight Is The Real Deal” was originally published on August 7, 2018.

The price of airfare is the number one reason why people don’t travel as much as they would like. So, when you spot a low fare to an international destination, it could feel like you’ve hit the travel lottery. But when is a cheap flight deal too good to be true?

The truth is that fares fluctuate throughout the day so the number of seats offered at the lowest prices will change frequently. There are times, however, when deals are simply too good.

“Earlier this year, the internet was abuzz over a $300+ fare to New Zealand, bookable from many U.S. cities,” said Tracy Stewart, editor and travel expert at travel deal site Airfarewatchdog.com “That’s a great fare but it was issued in error, which does happen from time to time. In this case, the airline didn’t honor the fare.”

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The good news is that if this happens to you, the U.S. Department of Transportation requires carriers to reimburse that expense along with any other non-refundable purchases you made as a result of the error ticket, according to Stewart.

“It’s always a good idea to hold off on making additional hotel or tour arrangements until you’re absolutely sure the airline plans to honor the ticket,” he said. “If you haven’t heard anything after 72 hours, you’re probably in the clear.”

Before booking what appears to be a flight deal, Stewart recommends that travelers take into account any ancillary fees that may apply.

Tameika Gentles, a nomadic fitness entrepreneur who has traveled to more than 40 countries, agreed.

“I’ve learned from experience that flights can seem cheap because everything else, like carry-ons, and luggage, is à la carte,” Gentles said. “After paying for everything, the flight isn’t that cheap.”

For the best deals on flights, Gentles said the key is remaining open.

“Be flexible both on your dates and destinations if you can,” she said. “Don’t forget to look at the whole picture. A flight to Vietnam may cost more, but you can live off less than $10 per day.”