please give me the flight times the morning on united airlines for september twentieth from philadelphia to san francisco
O O O O B-flight_time I-flight_time O B-depart_time.period_of_day O B-airline_name I-airline_name O B-depart_date.month_name B-depart_date.day_number O B-fromloc.city_name O B-toloc.city_name I-toloc.city_name