Database: airline
Question: Among the flights with air carrier described as Asap Air Inc.: ASP, what is the tail number of the flight with the longest departure delay?
SQL: SELECT T2.TAIL_NUM FROM `Air Carriers` AS T1 INNER JOIN Airlines AS T2 ON T1.Code = T2.OP_CARRIER_AIRLINE_ID WHERE T1.Description = 'Asap Air Inc.: ASP' ORDER BY T2.DEP_DELAY DESC LIMIT 1