The FAA tries to assign logical location identifiers. For all you ever wanted to know on the assigning of location identifiers, see http://www.faa.gov/ATPUBS/LID/LIDHME.htm One thing to note: Once assigned, there has to be a really good reason to change it. I'm still miffed that the authorities bowed down to the idiot politicians (yea, I know that's redundant) of Baltimore a few years ago and changed the Baltimore id from BAL to BWI. David R -------------- Original message -------------- > Any idea why FSD (Sioux Falls, South Dakota) has that airport code? > > My hunch is FSD = Falls South Dakota, but my hunch has been wrong > before... > > Blaine