What are the names of the airlines ?
select name from airlines
How many routes are there in the United States ?
select count ( * ) from routes as t1 join airlines as t2 on t2.alid = t1.alid where t2.country = 'United States'
Can you give me a number of routes per country and airline name  ?
select t1.country, t1.name, count ( * ) from airlines as t1 join routes as t2 on t1.alid = t2.alid group by t1.country, t1.name