instruction: what is the smallest aircraft that flies from PITTSBURGH to BALTIMORE arriving 5 7
response: SELECT DISTINCT aircraft.aircraft_code FROM aircraft, airport_service AS AIRPORT_SERVICE_0, airport_service AS AIRPORT_SERVICE_1, city AS CITY_0, city AS CITY_1, date_day, days, equipment_sequence, flight WHERE (((((flight.arrival_time < 41 OR flight.time_elapsed >= 60) AND flight.departure_time > flight.arrival_time) AND date_day.day_number = 6 AND date_day.month_number = 5 AND date_day.year = 1991 AND days.day_name = date_day.day_name AND flight.flight_days = days.days_code) OR (date_day.day_number = 7 AND date_day.month_number = 5 AND date_day.year = 1991 AND days.day_name = date_day.day_name AND flight.flight_days = days.days_code AND NOT ((flight.arrival_time < 41 OR flight.time_elapsed >= 60) AND flight.departure_time > flight.arrival_time))) AND CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'BALTIMORE' AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND aircraft.capacity = (SELECT MIN(AIRCRAFTalias1.capacity) FROM aircraft AS AIRCRAFTalias1, airport_service AS AIRPORT_SERVICEalias2, airport_service AS AIRPORT_SERVICEalias3, city AS CITYalias2, city AS CITYalias3, date_day AS DATE_DAYalias1, days AS DAYSalias1, equipment_sequence AS EQUIPMENT_SEQUENCEalias1, flight AS FLIGHTalias1 WHERE (((((FLIGHTalias1.arrival_time < 41 OR FLIGHTalias1.time_elapsed >= 60) AND FLIGHTalias1.departure_time > FLIGHTalias1.arrival_time) AND DATE_DAYalias1.day_number = 6 AND DATE_DAYalias1.month_number = 5 AND DATE_DAYalias1.year = 1991 AND DAYSalias1.day_name = DATE_DAYalias1.day_name AND FLIGHTalias1.flight_days = DAYSalias1.days_code) OR (DATE_DAYalias1.day_number = 7 AND DATE_DAYalias1.month_number = 5 AND DATE_DAYalias1.year = 1991 AND DAYSalias1.day_name = DATE_DAYalias1.day_name AND FLIGHTalias1.flight_days = DAYSalias1.days_code AND NOT ((FLIGHTalias1.arrival_time < 41 OR FLIGHTalias1.time_elapsed >= 60) AND FLIGHTalias1.departure_time > FLIGHTalias1.arrival_time))) AND CITYalias3.city_code = AIRPORT_SERVICEalias3.city_code AND CITYalias3.city_name = 'BALTIMORE' AND FLIGHTalias1.to_airport = AIRPORT_SERVICEalias3.airport_code) AND CITYalias2.city_code = AIRPORT_SERVICEalias2.city_code AND CITYalias2.city_name = 'PITTSBURGH' AND EQUIPMENT_SEQUENCEalias1.aircraft_code = AIRCRAFTalias1.aircraft_code AND FLIGHTalias1.aircraft_code_sequence = EQUIPMENT_SEQUENCEalias1.aircraft_code_sequence AND FLIGHTalias1.from_airport = AIRPORT_SERVICEalias2.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'PITTSBURGH' AND equipment_sequence.aircraft_code = aircraft.aircraft_code AND flight.aircraft_code_sequence = equipment_sequence.aircraft_code_sequence AND flight.from_airport = AIRPORT_SERVICE_0.airport_code