Carriers Cut Fares: Three of the nation's airlines kicked off a fare sale, discounting tickets through the end of the summer season. Northwest Airlines will offer passengers up to 40% off regular excursion fare levels for travel in the continental United States. The carrier said discounts are also available for travel to Alaska, Canada, the Caribbean, Mexico and Hawaii. Tickets must be purchased by Wednesday for travel through Sept. 14. The non-refundable fares require a 21-day advance purchase, Northwest said. Many airlines quickly matched Northwest's discount--including American Airlines, United Airlines, Trans World Airlines and USAir. Separately, America West Airlines announced it will offer passengers up to $80 or about 20% off selected medium- and long-haul flights. Tickets must be purchased by Wednesday for travel through Sept. 14.