As far as can be ascertained, the motto of the Royal Air Force dates back to 1912 and the formation of the Royal Flying Corps (RFC). The first Commanding Officer of the RFC (Military Wing) was Colonel Frederick Sykes. He asked his officers to come up with a motto for the new service; one which would produce a strong esprit de corps.
Shortly after this, two junior officers were walking from the Officers' Mess at Farnborough to Cody's Shed on Laffan Plain. As they walked, they discussed the problem of the motto and one of them, JS Yule, mentioned the phrase "Sicictar ad Astra", from the Virgilian texts. He then expanded on this with the phrase "Per Ardua ad Astra", which he translated as, "Through Struggles to the Stars". Colonel Sykes approved of this as the motto and forwarded it to the War Office. It was then submitted to the King, who approved its adoption.
The question of where this motto had come from can be answered by he fact that Yule had read it in a book called "People of the Mist" by Sir Henry Rider Haggard. In the first chapter was the passage, "To his right were two stately gates of iron fantastically wrought, supported by stone pillars on whose summit stood griffins of black marble embracing coats of arms and banners inscribed with the device 'Per Ardua ad Astra'".
As to where Sir Rider Haggard obtained this phrase is still unclear although it is possible that it originated from the Irish family of Mulway who had used it as their family motto for hundreds of years and translated it as "Through Struggles to the Stars".
The authoritative translation of the motto is just as unsure as the source. Since there can be a number of different meanings to 'Ardua' and 'Astra', scholars have declared it to untranslatable. To the Royal Air Force and Commonwealth Air Forces though it will remain "Through Struggles to the Stars". It is peculiar to the Royal Air Force and has been made famous by the heroic and courageous deeds of our air forces over the years.