What are the different pilot names who had piloted a flight in the country 'United States' or in the airport named 'Billund Airport'?
return pilots ;return countries #1 piloted flights in ;return #1 where #2 is  'United States ;return airports #1 piloted flights in ;return #1 where #4 is  'Billund Airport ;return #3 or  #5 ;return different names of #6
['select', 'project', 'comparative', 'project', 'comparative', 'union', 'project']