This week Southwest Airlines began offering DING! fares to & from San Francisco airport.DING! is an online application which alerts subscribers to special Southwest Airline airfare deals - deals not even found on their own website. DING, named because of the familiar ding chime heard on airplanes, often releases deals once or twice a day and usually must be purchased that day. Oakland, San Jose and Sacramento airports have listings daily, and now San Francisco was just added to the daily digest as well. More information on DING! can be found here.