instruction: what is the earliest flight between BOS and BWI
response: SELECT DISTINCT flight.flight_id FROM airport AS AIRPORT_0, airport AS AIRPORT_1, flight WHERE (AIRPORT_0.airport_code = 'BOS' AND AIRPORT_1.airport_code = 'BWI' AND flight.from_airport = AIRPORT_0.airport_code AND flight.to_airport = AIRPORT_1.airport_code) AND flight.departure_time = (SELECT MIN(FLIGHTalias1.departure_time) FROM airport AS AIRPORTalias2, airport AS AIRPORTalias3, flight AS FLIGHTalias1 WHERE AIRPORTalias2.airport_code = 'BOS' AND AIRPORTalias3.airport_code = 'BWI' AND FLIGHTalias1.from_airport = AIRPORTalias2.airport_code AND FLIGHTalias1.to_airport = AIRPORTalias3.airport_code)