As frequent flyers become more and more Web-savvy, self-service, online booking has become widespread (the occasional bonuses don’t hurt).

But when you find yourself ready to book that trip, be sure you know where you want to go.

According to The Associated Press, about once a month, a passenger who had expected to step off the plane in Lafayette, La., shows up at Purdue University Airport in west-central Indiana.

The problem apparently lies with travelers who use the Internet to book flights and choose the wrong three-letter airport code, confusing West Lafayette’s LAF code for Lafayette, La., which has LFT as its code.

“You get on Travelocity or one of those sites, the first Lafayette code it gives you is LAF,” Jason Devillier, deputy administrator of the Lafayette Regional Airport in Louisiana told The Associated Press.

Devillier said the problem with misdirected fliers was more frequent when Northwest Airlink had operations at the Purdue airport, because the airline served both Lafayettes until it pulled out of Purdue in December.

Similar problems have occurred at airports in Grand Rapids, Mich., and Grand Rapids, Minn., as well as in Rochester, Minn., and Rochester, N.Y., and other U.S. cities.