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
비행기의 보조익은 비행 안정성을 높이는 데 도움을 줍니다.bihaenggiui bojoik-eun bihaeng anjeongseong-eul nopineun de doum-eul jubnida.The auxiliary wing of the aircraft helps to improve flight stability.