i'd like to see flights from baltimore to atlanta that arrive before noon and i'd like to see flights from denver to atlanta that arrive before noon 
return flights  ;return #1 from baltimore ;return #2 to  atlanta ;return #3 that  arrive  before noon  ;return #1 from denver ;return #5 to  atlanta ;return #6 that  arrive  before noon  ;return #4 ,  #7
['select', 'filter', 'filter', 'filter', 'filter', 'filter', 'filter', 'union']