What are the names of all aircrafts that are associated with both London Heathrow and Gatwick airports?
select t1.aircraft from aircraft as t1 join airport_aircraft as t2 on t1.aircraft_id = t2.aircraft_id join airport as t3 on t2.airport_id = t3.airport_id where t3.airport_name = "London Heathrow" intersect select t1.aircraft from aircraft as t1 join airport_aircraft as t2 on t1.aircraft_id = t2.aircraft_id join airport as t3 on t2.airport_id = t3.airport_id where t3.airport_name = "London Gatwick"