Have you ever taken advantage of a suspiciously low airfare — say $300 to Europe in business class — that turned out to be a mistake? Did the airline cancel your ticket or did you fight to keep it? If you gave in, it might have been premature.

Like any human activity, filing fares is prone to errors once in a while — a few times a year at most, which is too much for the airlines, but not enough if you ask bargain-hunting travelers. In the most recent reported example, on Dec. 27, a traveler looking for a ticket stumbled upon a Swiss International Airlines business class fare of $0 plus tax from Toronto to several European cities. It was available on various booking engines, including Swiss’ Web site and Travelocity…