It's in the Air (1938)

George Brown is rejected as an Air Raid Warden and in doing so sees his potential to join the Royal Air Force. His dreams could soon come true as he realises that in fact his friend has left behind some very important papers, he dons a his Royal Air Force uniform and delivers the papers when he is mistaken for a dispatch driver from HQ. He soon becomes the butt of jokes from his sergeant which ends him staying indefinitely at the air base. George soon falls in love with the Sergeant Major's daughter and when he discovers his real identity he threatens to report him. On the day of an annual inspection George attempts to escape the base and ends up in a plane, while the inspecting officer watches on, George's plane display is mesmerizing and the inspecting officer insists he should be commended, in order to save their skins George manages to land the plane and is accepted as a flyer by the RAF.

Source: TMDb