please show me united nonstop flights between boston and san francisco departing around 5 in the evening 
return flights ;return #1 that  are nonstop ;return #2 on  united ;return #3 from  boston ;return #4 to san francisco ;return #5 departing around 5 in the evening
['select', 'filter', 'filter', 'filter', 'filter', 'filter']