First flown in August 1926, the LéO 21 was a large airliner based on the LéO 20 night bomber. It could carry 18 pax but on Air Union's Rayon d'Or / Golden Ray service from Paris to London it seated twelve, with a galley occupying the nose. The second prototype, designated LéO 212, is seen departing in a national air rally to the Auvergne, flown by Air Union chief pilot Robert Bajac.