Originally Posted by
walukanis
Can somone explain why any route would ever be illegal (other than through Cuba or N. Korea) ?
Illegal is a questionable term to use, but it is the one in the vernacular. There are rules within each FF program about what routes are permitted for various trips. Some have to follow published fare routing rules, some are based on IATA MPM numbers and some are just based on the city pair and regions transited.