Airlines are among the few businesses that sometimes want customers to pay for their mistakes. Every once in a while, a carrier cancels issued tickets after it deems its own published fare was an “error.” The Department of Transportation tried to teach such companies a lesson last week — sort of.

Both U.S. and foreign airlines have filed mistake fares in recent years, as has been reported in this column. Some of the airlines, such as United Airlines and Alitalia, have honored purchased tickets, but others, such as Swiss International Airlines, have not. The DOT’s Wednesday ruling was directed at British Airways…