i have two friends that would like to visit me on wednesday here in washington dc one of them lives in denver and the other lives in miami 
return flights ;return #1 from  denver ;return #2 to washington dc ;return #3 on  wednesday ;return #1 from  miami ;return #5 to washington dc ;return #6 on  wednesday ;return #4 , #7
['select', 'filter', 'filter', 'filter', 'filter', 'filter', 'filter', 'union']