Database: flight_2
Question: Find all airlines that have flights from both airports 'APG' and 'CVO'.
SQL: select t1.airline from airlines as t1 join flights as t2 on t1.uid  =  t2.airline where t2.sourceairport  =  "apg" intersect select t1.airline from airlines as t1 join flights as t2 on t1.uid  =  t2.airline where t2.sourceairport  =  "cvo"