America West Airlines has marked its return to Washington National Airport by offering an Internet fare sale, the company said Monday. Closed after the Sept. 11 terrorist attacks on New York and the Pentagon, America West recently resumed service at the airport in the nation's capital. Since the attacks, the airlines have launched several fare wars. The airlines have cut online fares the most as they try to coax passengers to buy over the Net, a less expensive distribution channel than when a customer orders from a travel agent. Roundtrip tickets must be purchased at Americawest.com by Dec. 2 for travel between Dec. 3 and Feb. 14, 2002, the company said in a statement.