Not even a full cruise season after the mechanics' and groundworkers' strike against Northwest Airlines illustrated just how dependent we are on one Goliath airline, this upstart vacation charter company announced its decision to start scheduled service from here to ten U.S. cities. Sun Country's flight schedules are a little odd and its planes are crowded, but fares are rock-bottom and there's virtually none of that advance-purchase discount dance that takes the fun out of a weekend escape from the snow or the kids. Sun Country swears none of this will change once the switch to scheduled service is made in June. Airline administrators are hoping to move from the airport's charter annex into the main terminal, but we happen to like 'em right where they are: Travelers leaving from the Hubert H. Humphrey Terminal can park within 50 feet of their gate, and the place has pretty much every convenience one could possibly need between check-in and take-off. The only cloud on the horizon is NWA's inevitable move to stomp on the little-guy interlopers; the opening salvos are already being fired. All we can say is: Fly 'em or lose 'em, folks.