Which airports do not have departing or arriving flights?
return airports ;return departing flights of #1 ;return number of  #2 for each #1 ;return #1 where #3 is zero ;return arriving flights of #1 ;return number of  #5 for each #1 ;return #1 where #6 is zero ;return #1 in  both #4 and  #7
['select', 'project', 'group', 'comparative', 'project', 'group', 'comparative', 'intersection']