Error fares usually come from a currency conversion mistake, a missing fuel surcharge, or a fare-class typo somewhere in an airline's pricing system. They're rare, they're unannounced, and they typically get corrected within hours — sometimes minutes — of being discovered, which is why deal communities and fare-alert tools exist specifically to catch them fast.
Airlines are not legally required to honor an error fare everywhere, though in several countries (including transactions confirmed and ticketed in the US) airlines have historically honored mistake fares once a booking is fully confirmed and paid. That said, some bookings do get cancelled with a refund, so it's smart to treat an error fare as a probable win rather than a guaranteed one until it's ticketed.
The fastest way to catch a mistake fare is a flexible-date, flexible-destination mindset paired with fast-moving fare-alert tools or deal-community feeds. Because these fares vanish quickly, the travelers who benefit most are usually the ones who book first and ask questions later — within the airline's normal cancellation window, of course.
If you do book what looks like an error fare, avoid calling the airline to "confirm" it before your booking is fully ticketed — that sometimes accelerates the airline noticing and correcting the mistake. Wait for your e-ticket confirmation number, then double-check your card wasn't charged an unusual amount.
