We didn't think it particularly appropriate for Continental to be telling us that we shouldn't be offering reduced fares to people in Minneapolis and the Upper Midwest, and so we essentially tried to tell them to knock it off and leave us alone." To do that, he said Northwest then sent its own message. It filed into the Airline Tariff Publishing network new cheap fares from Houston to the West Coast, again with short expiration dates. Houston is a critical base for Continental, a unit of Continental Airlines Holdings Inc.