For the flight from ATL to PHL on 2018/8/1 that scheduled local departure time as "2040", which air carrier does this flight belong to?
flight from ATL refers to ORIGIN = 'ATL'; flight to PHL refers to DEST = 'PHL'; on 2018/8/1 refers to FL_DATE = '2018/8/1'; local departure time refers to CRS_DEP_TIME; CRS_DEP_TIME = '2040';
SELECT T2.Description FROM Airlines AS T1 INNER JOIN `Air Carriers` AS T2 ON T1.OP_CARRIER_AIRLINE_ID = T2.Code WHERE T1.FL_DATE = '2018/8/1' AND T1.ORIGIN = 'ATL' AND T1.DEST = 'PHL' AND T1.CRS_DEP_TIME = '2040' GROUP BY T2.Description