What airline serves the most flights?
SELECT T1.Airline FROM AIRLINES AS T1 JOIN FLIGHTS AS T2 ON T1.uid  =  T2.Airline GROUP BY T1.Airline ORDER BY count(*) DESC LIMIT 1
SELECT T1.Airline FROM AIRLINES AS T1 JOIN FLIGHTS AS T2 ON T1.uid  =  T2.Airline GROUP BY T1.Airline ORDER BY count(*) DESC LIMIT 1
[{'Airline': 'Virgin America'}]