Though the ability of retractable leading edge slots to enable wings to reach high angles of attack without stalling and hence allow low flying speeds without a high speed drag penalty was discussed at the 1921 Paris Salon by Frederick Handley Page,[1] slats were not used by French military aircraft before the 1928 Villiers XXIV.

Apart from a small centre section with a large cut-out to improve the visibility from the pilot's cockpit, the whole of the trailing edge was filled by flaps inboard and ailerons outboard.

When the slats were opened by the pilot, ailerons and flaps were depressed but retained their normal functions with unchanged angular defection ranges.

[3] The Villier XXIV's fuselage was built around six longerons, positioned by glued formers, and plywood covered behind the nose where its 340 kW (450 hp) Lorraine 12Eb Courlis water-cooled W-12 engine was under an aluminium cowling which followed the outlines of the three cylinder banks.

[2] The tail unit was conventional, with a broad chord, clipped triangular tailplane, mounted on top of the fuselage at an angle which could be adjusted in flight and fitted with separate, round edged, balanced elevators.