Chron.com | Southwest Airlines nonstop flight sale ends Monday, Sept. 19 Chron.com There are also limits on certain flights, per the sale site: "Travel to Cancun, Cabo San Lucas/Los Cabos and Puerto Vallarta is valid only on Sundays through Wednesdays. Travel from Cancun, Cabo San Lucas/Los Cabos and Puerto Vallarta is valid only on ... |