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
고도비행은 비행기의 성능을 시험하는 데 중요합니다.godo bihaeng-eun bihaenggi-ui seongneung-eul siheomhan-eun de jungyohamnida.Altitude flight is important for testing the performance of an aircraft.