DALLAS, June 21 —Just in time for the first day of summer, Southwest Airlines (NYSE LUV) is launching a Vacation Destination Giveaway through the airline’s frequent flyer program, Rapid Rewards. The eight-week promotion begins today and runs through August 15, 2010. Members will have a daily opportunity to answer Rapid Rewards trivia questions and play an instant win game with prizes including Rapid Rewards credits and free (See Terms and Conditions below) roundtrip tickets. The promotion will also feature....