More than 6.6 million people in Chicago and the surrounding region, including parts of Indiana, were under tornado watches and warnings on Tuesday evening as severe storms battered the area, according to the National Weather Service.The storms prompted officials at O’Hare International Airport to briefly ground all departing flights and suspend its rail service on Tuesday evening while asking people in the airport to “exercise caution.”The NBC News affiliate in Chicago shared video of hundreds of passengers packing into the airport for shelter.An early picture of the damage inflicted…