Southwest Airlines is offering members of itsfrequent flyer program double points on flights to/from Baltimore-Washington International Thurgood Marshall Airport.Travelers musttheir flights and traveling by Nov. 7.Southwest's promotion also offers double points for travel to Denver and Phoenix.recently announced that the airport had its best July ever, in terms of the number of passengers, serving some 2.2 million fliers. Of those, 1.2 million were customers of Southwest, which also scored a record for the month of July in Baltimore.