First flown in August 1929 the LéO 21 was a twin-engined biplane airliner with a fixed tailskid landing gear.

It retained the basic structure of the LéO 20 night bomber but with a new wider fuselage.

The first production LéO 213 was built in 1928 and a total of eleven were built and operated by Air Union on routes from Paris to London, Lyons, Marseilles and Geneva.

The LéO 213 had an increased wingspan, improved sound proofing and three baggage holds.

In 1934 all the surviving LéO 213s were bought by the Armée de l'Air (French Air Force) and were converted to transports for 14-troops on bench seats and re-designated LéO 214.