Destinations worldwide are available in this sale. Travel periods and expiration dates vary by route. Chicago departures are available for winter travel January-March. Washington D.C. departures are mostly for February travel and Houston departures are for Spring travel April-May, but this does vary, so be sure to read the fare details for any given route. Sale fares from Chicago are set to expire tonight, Dec. 31, 2013. Sale fares from other departure cities could expire at anytime.