[3] Development of what would become the Potez 39 was heavily shaped by a period of methodical study conducted at Méaulte under the direction of the aeronautical engineer Louis Coroller; this was initially carried out on conventional monoplanes before progressing to metal aircraft that were adapted for quantity production.

The Potez 39 was a dedicated aerial reconnaissance aircraft that featured all-metal construction, which included the coverings of both the fuselage and wings.

[5] The latter, which was composed of duralumin sheeting, was attached to the fuselage proper via four spherical fittings that were bolted to the forward ends of the longerons.

The former was supported via a trellis girder arrangement, comprising varying thicknesses of duralumin, the uprights and diagonals of which were joined via simple riveted gussets to the longerons.

Extensive testing was performed by Potez to determine that these proportions provided sufficient rigidity without overly increasing friction.

The internal structure of the wing comprised two spars with diagonal bracing (using duralumin half-tubes) and widely spaced ribs.

[9] The main undercarriage, which had a track gauge of 3 m (9.84 ft.) and was furnished with wheel brakes, was of an axleless design that incorporated Potez's own elastic struts.

[9] The rear of the stabiliser was attached to a movable support that permitted mid-flight adjustments with relatively little force via an arrangement of flexible joints and ball bearings.

The elevator, which was positioned in front of the rudder, was unbalanced, slightly tapered, and had well-rounded tips; its structure was akin to that of the wing as well as covered by duralumin.

[14] In August 1938, during the Munich Crisis,General Joseph Vuillemin, Chief of Staff of the French Air Force, gave orders that, in the event of war breaking out, obsolescent observation aircraft such as the Potez 39 should never cross the front line.

[15] At the outbreak of the Second World War, the Potez 39 was in service with seven GAOs, which despite their age and Vuillemin's 1938 instructions, were deployed on operational missions.

[19] The outbreak of the Second World War stopped deliveries of spare parts and technical assistance from France, and the type was phased out from active service.