show names of all aircrafts?
select name from aircraft
in which aircraft does John Williams have a certificate
select t3.name from employee as t1 join certificate as t2 on t1.eid = t2.eid join aircraft as t3 on t3.aid = t2.aid where t1.name = "John Williams"
give me the airline id to that
select t3.aid from employee as t1 join certificate as t2 on t1.eid = t2.eid join aircraft as t3 on t3.aid = t2.aid where t1.name = "John Williams"