The four-engined Lioré et Olivier LeO H-27 was one of three French flying boats competing to carry mail over Air France's South Atlantic routes.

The LeO H-27 was built in response to a French government call for a postal aircraft able to cover the South Atlantic routes.

The outer panel tapered in thickness outwards and carried 11.80 m (38.7 ft) span ailerons which, like the rear control surfaces, were balanced.

The wing was built around two duralumin spars joined into a central box to which the leading and trailing edges were attached; all were dural covered.

It had side-by-side seats with dual controls and was high up, with a navigator's cabin and radio equipment underneath, lit by portholes just forward of the port side crew entry door.