Question: What type of aircraft was introduced in 1988 and is currently flown by Virgin America?
Answer(s):
answer: Airbus A320

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.03bwrn)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.03bwrn ns:aviation.aircraft_owner.aircraft_fleet_composition ?y .
?y ns:aviation.aircraft_ownership_count.aircraft_model ?x .
?x ns:aviation.aircraft_model.introduced "1988"^^xsd:dateTime . 
}