Southwest Airlines is now offering service from O’Hare Airport. The airline started nonstop flights yesterday to Baltimore, Dallas, Denver, Nashville and Phoenix at the Chicago airport. Starting March 13th, Southwest will also begin Saturday-only service to Orlando. The airline has already operated from Midway Airport since 1985. Though Southwest has begun service from O’Hare, Midway will remain its primary Chicago airport. Southwest offers up to 200 flights a day from Midway.