A mistake fare can work in your favor, but here's what you need to know before you book a flight that seems too good to be true.

A Cathay Pacific plane taking shortly after takeoff from Hong Kong airport
Credit: Marcio Rodrigo Machado/S3studio/Getty Images

Earlier this week, would-be passengers on Cathay Pacific Airways flights were stunned to find first class tickets going for as low as $675 for routes between Vietnam and Canada and Vietnam and the United States. No, their eyes weren’t deceiving them. The prices really were that low.

It turns out the prices were that low due to a mistake — but those smart enough to book the flights anyway were handsomely rewarded on Wednesday when the airline announced it would indeed honor the fares.

“We do not want to go back on our promise to our customers,” Cathay announced on its Twitter account. “We made a mistake but we look forward to welcoming you on board with your ticket issued.”

So how much money are these passengers really saving? According to Gary Leff, a travel and loyalty-program blogger on View from the Wing, the same first and business class round-trip tickets from Da Nang to New York that started at $675 are now on sale for $16,000.

Cathay Pacific is far from the only airline to ever make a mistake fare public. According to Fortune, in 2014 Singapore Airlines published and honored its own mistakes while Hong Kong Airlines honored business class tickets mistakenly sold at economy fares in 2018.

These fares are also referred to as “fat finger” fares. As the name implies, the mistake can be a human error when someone misplaces a decimal point in the system, or it can be due to a miscalculated currency conversion, data entry error, or simply a computer glitch.

Travelers can book these fares on sites like Kayak or Expedia, though the team at Scott’s Cheap Flights recommends people book directly through the airline whenever possible.

However, everyone should be warned that airlines are under no obligation to honor the fares. They are obligated to reimburse all out-of-pocket expenses made in confidence upon the reservation, according to USA Today. That means travelers are entitled to a full refund for the cost of the errant ticket along with all non-refundable purchases made after booking the mistake fare. But, who knows, maybe you’ll get as lucky as these Cathay Pacific passengers too.