Database: flight_2
Question: How many United Airlines flights go to City 'Aberdeen'?
SQL: select count(*) from flights as t1 join airports as t2 on t1.destairport  =  t2.airportcode join airlines as t3 on t3.uid  =  t1.airline where t2.city  =  "aberdeen" and t3.airline  =  "united airlines"