instruction: locate flights from PHILADELPHIA to DALLAS stopping in ATL
response: SELECT DISTINCT flight.flight_id FROM airport, airport_service AS AIRPORT_SERVICE_0, airport_service AS AIRPORT_SERVICE_1, city AS CITY_0, city AS CITY_1, flight, flight_stop WHERE (airport.airport_code = 'ATL' AND CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'DALLAS' AND flight_stop.stop_airport = airport.airport_code AND flight.flight_id = flight_stop.flight_id AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'PHILADELPHIA' AND flight.from_airport = AIRPORT_SERVICE_0.airport_code