The Royal Canadian Air Force used it until 1968, when it adopted the motto sic itur ad astra, a similar phrase meaning "such is the pathway to the stars".
As they walked they discussed the problem of the motto and one of them, Lieutenant J. S. Yule, mentioned the phrase Sic itur ad Astra, from Virgil.
[4] Yule is believed to have borrowed the phrase from Sir Henry Rider Haggard's fantasy novel The People of the Mist (1894).
The first chapter includes the sentence: "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'".
[5] The motto of the Royal Air Force Regiment omits the ad astra part, becoming simply per ardua.