CREATE TABLE aircraft (aid NUMBER, name CLOB, distance NUMBER)
CREATE TABLE employee (eid NUMBER, name CLOB, salary NUMBER)
CREATE TABLE flight (flno NUMBER, origin CLOB, destination CLOB, distance NUMBER, departure_date TIME, arrival_date TIME, price NUMBER, aid NUMBER)
CREATE TABLE certificate (eid NUMBER, aid NUMBER)

Show names for all aircraft with at least two flights.
SELECT T2.name FROM flight AS T1 JOIN aircraft AS T2 ON T1.aid = T2.aid GROUP BY T1.aid HAVING COUNT(*) >= 2
SELECT "T2"."name" FROM "flight" "T1" JOIN "aircraft" "T2" ON "T1"."aid" = "T2"."aid" GROUP BY "T1"."aid" HAVING COUNT(*) >= 2