This post contains references to products from one or more of our advertisers. We may receive compensation when you click on links to those products. The content on this page is accurate as of the posting date; however, some of the offers mentioned may have expired. For more information check out our Advertising Disclosure. Picture this: After seeing flight prices to Europe this summer north of $1,000, you hear whispers (or maybe catch a glimpse of an alert from your favorite flight deal service) of flights to Dublin (DUB) for under $150 roundtrip. No way. It couldn't be that cheap, right?

It's real. Look at this.

Welcome to the wild, thrilling world of mistake fares: the undisputed gold standard of flight deals.

Want to save hundreds, if not thousands, on your plane ticket? Looking to fly business class without paying a fortune? It's a mistake fare you're looking for, the ridiculously cheap fares that pop up when you guessed it an airline mistakenly sells a fare for cheap.

These kind of errors are rare and unpredictable: You never know when the next one will appear. Over the last several years, we've found $63 roundtrip fares to Santiago de Chile (SCL), $229 flights to Paris or $238 to Croatia and back, and even a business class fare to Asia and back for under $700 when it should have cost $7,000. But then you can go months, even a year, without even a whiff of another error.

It happened again this week.

Roundtrip fares to Dublin that should have been sold for $900 or more were bookable for just $148 or $200 from Minneapolis-St. Paul (MSP) and Chicago-O'Hare (ORD), respectively. This unreal deal disappeared within a matter of hours, but not before hundreds ofThrifty Traveler Premium members booked dirt-cheap trips to Ireland this summer or fall.

Get an instant alert for the next mistake fare with Thrifty Traveler Premium!

So what's really behind these ultra-cheap flights? How rare are they? And how can you get in on the next one? Read on.

What is a Mistake Fare? These fares are just what they sound like. For one reason or another, airlines sell tickets at a cheaper price than they intended. If you see a plane ticket that looks too good to be true, it could be a mistake fare.

Maybe it's the result of an error in converting different currencies. The airline might have accidentally left an important surcharge off the final ticket price. Sometimes, it's as simple as an employee hitting the wrong number or missing a zero as they enter a fare.

Mistake fares are also one of the few ways to snag a barnburner deal on business or first class plane tickets, like the mistake fare to fly Cathay Pacific First Class for less than $1,000 we found a few years ago. Competition for top-dollar customers is so tight and so motivated by big money, airlines rarely sell those seats at huge discounts.

In business class or economy, airlines have gotten better and better at detecting their mistakes quickly or catching them before they're published. What was once a steady stream of two or three mistake fares a year has slowed to a trickle.

But they still happen.

How Do You Find Mistake Fares? By their very nature, mistake fares are unpredictable. You could scour the internet for hours on end every day all year and not find one of these insanely cheap mistake fares.

Let us do the work for you. Thrifty Traveler Premium subscribers get the first scoop on these mistake fares. We send out alerts for mistake fares within minutes of finding them and round up other mistake fares making the rounds on the internet.

Thrifty Traveler Premiummembers got the first crack at booking that $13,500 first-class ticket from Vietnam to the U.S. and back for under $1,000 a few years ago. They also got a chance to book a trip from the U.S. to Chile for just $200 normally a $1,000-plus ticket.

But just when we thought we'd seen the greatest Chile fare ever, our team uncovered one of the best mistake fares we've ever seen in 2020.

No Photoshop, we swear! This was an actual fare that Delta published and that we booked in 2020! Fly to Chile and back, nonstop on Delta, for $63. While nonstops were available from Atlanta (ATL), you could hop on flights down to Chile from Minneapolis-St. Paul (MSP) for $186 roundtrip or get there and back from Orlando (MCO) for $147 along with sub-$300 fares from dozens of U.S. cities.

At the same time, we also unearthed flights to Lima, Peru starting at just $111 roundtrip, also on Delta. It was a whirlwind couple of days at Thrifty Traveler Premium, but our subscribers were rewarded for it.

How Do I Book Mistake Fares? One word: Quickly.

There's no telling how long a mistakenly discounted fare will be on sale before it's pulled. It varies by how good the deal is and how long the airline takes to catch its mistake. If you want to get the best deal, act fast!

We've seen some of the best mistake fares disappear within minutes of going on sale. A mistake fare from Miami (MIA) to Fortaleza, Brazil (FOR) for an astounding $132 disappeared less than 30 minutes after we first saw it. Others have lasted close to an entire day or longer. Long story short, don't count on that insane flight deal sticking around for long.

When it comes to mistake fares, it's imperative to act fast. For example, Thrifty Traveler Premium members were treated to this mistake fare to fly in lie-flat business class seats to London-Heathrow (LHR) for about $900 roundtrip! That's more than $2,000 off the usual price, so go figure it only lasted an hour or two!

So if you see a great mistake fare here or elsewhere on the internet, don't go back and forth with your travel companion or boss about whether or not you can take the trip.Book now and ask questions later.If it turns out you can't use the cheap ticket you just bought, you have 24 hours to cancel it for a full refund. The U.S. government requires this refund policy for any flight that touches U.S. soil, so use it.

But there's also a chance the airline won't even honor the fare (more on this in a bit). So just as important as booking the fare fast is to not book anything else. Don't pay for any nonrefundable hotels, tours, excursions, rental cars, or other pieces of your vacation until you know your ticket is safe. Odds are, you won't get anything official from the airline unless your ticket is canceled. So if it's still in your account after two weeks and you haven't heard from the airline that they're invalidating your flight, you're probably safe to plan the rest of your trip.

It may seem counterintuitive, but after buying your ticket on impulse, be patient.

Will the Airline Honor These Fares? This is the million-dollar question or, perhaps more accurately, the $148 question.

Unfortunately, it's a mixed bag. The U.S. government no longer requires airlines to honor the mistake tickets they sell if they can prove the pricing was offered due to an error. Airlines can cancel the fare so long as they fully refund the cost of the ticket.

Ultimately, it's largely the airline's choice whether to honor these fares. And that's never a sure thing. The best mistake fares we've seen in the last few years show it's unpredictable.

Two of our favorite crazy flight deals from way back in 2018 were mistake fares that the airlines chose to honor. The $238 round-trip tickets from the U.S. to Croatia took the internet by storm, and we found it first. And amazingly, American Airlines decided to honor the fare that normally sells for $1,200 or more. We know plenty of Thrifty Traveler Premium members got in on this deal and scored an insane deal to go explore Croatian wonders like Dubrovnik, Split, and Plitvice Lakes.

But it got even better. In one of the best mistake fares of all time, Hong Kong Airlines sold $560 roundtrip tickets in business class from Los Angeles (LAX) and San Francisco (SFO) to Bangkok (BKK), Shanghai (PVG), and Ho Chi Minh (SGN). These tickets normally cost close to $6,000 or more. And yet the airline decided to honor the tickets.

One of our favorite mistake fares of 2019 was a business class mistake fare to both Australia and New Zealand. For just $1,491 (a standard price of an economy flight to Australia), you could have gotten lounge access, and a business class seat including priority boarding, champagne, and lie-flat seats. The cost of this luxury experience is typically over $7,000.

More recently, the string of mistake fares has panned out for the travelers who snagged them. Those $62 Delta fares down to Chile in late 2020 went off without a hitch. Same goes for those $900 business class fares to London a few years ago, helping travelers get away with a massive business class bargain.

Only time will tell whether this latest Ireland deal will move forward. Three days after we uncovered those $148 to $200 fares, things are looking good.

But other would-be mistake fare flyers over the years weren't so lucky. Those crazy fares from Miami to Brazil for $132 were canceled shortly after booking. Air New Zealand once published an insane deal for $328 to fly round-trip from the U.S. to New Zealand flights that normally cost $1,100 and up. But the airline canceled all those tickets, scrapping traveler's dreams of a cheap way to explore New Zealand.

That's the life of a mistake fare flyer. The only thing you can do is wait and see and hope.

Bottom Line Trying to work out when a mistake fare will pop up and whether the airline will honor it is nearly impossible.

Do what you can to get in on these deals: Book fast, be patient, and wait with bated breath to see whether your ticket is confirmed.