Question: Which Southwest Airlines hub is closest to the city of Chicago?
Answer(s):
answer: Chicago Midway International Airport

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.01_d4)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.01_d4 ns:location.location.nearby_airports ?x .
?x ns:location.location.containedby ns:m.01_d4 .
?x ns:aviation.airport.airlines ?c .
?c ns:aviation.airline_airport_presence.airline ns:m.0gztl . 
}