Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
항공관제원은 비행기의 안전한 이착륙을 돕습니다.hanggonggwanje-woneun bihaenggaui anjeonhan ichakryugeul dopseumnida.The air traffic controller assists in the safe takeoff and landing of aircraft.