Chicago Midway International Airport ( airport code KMDW ) is a secondary airport serving the city of Chicago , Illinois . Chicago Midway International Airport , also known simply as Midway Airport or Midway , is an airport in Chicago , Illinois , United States , located on the city 's southwest side , eight miles ( 13 km ) from Chicago 's Loop . The airport 's current IATA code MDW has been in use since it was implemented in 1949 when Chicago Municipal Airport was renamed Chicago Midway Airport , although the airline schedule books continued to call it CHI until airline flights began at O'Hare .