The seaplane version, the Latécoère 28-3, was the first to make a postal delivery crossing of the South Atlantic when Jean Mermoz flew from Dakar to Natal in 21 hours and a half aboard the Comte-de-La Vaulx (prototype n° 919) on 12 May 1930.

Early examples had been furnished with Renault 12Jbr engines; however, all use of this powerplant was quickly substituted for by Hispano Suiza 12, which waw capable of providing up to 500 hp (370 kW).

The fuselage, which was highly streamlined and largely supported by light-metal tubing, was internally divided into three sections, each with its own distinct structure and function.

[1] The main landing gear comprised two independent wheels mounted on axles joined to the fuselage and supported by elastic struts that incorporated shock absorbers.

[2] The forwardmost section of the aircraft was the bow, the double tubular framework of which constitutes the engine bed in the form of a girder cradle.

Two struts are used to deliver power to the propeller, while various accessories of the engine, including the radiator, fire extinguishers, control lines, fuel piping, and oil tank.

The chief pilot would be seated on the left, provisioned with an instrument board complete with electric light switches, while the position on the right was equipped with a radio set.

[6] The rear section comprised a relatively simple arrangement of four girders that supported the tail unit; these were braced with piano wires and enclosed in a light wood cowling.

[3] The wing of the Latécoère 28, which was furnished with a pair of ailerons and elliptical wingtips, was rigidly attached to the fuselage via a set of oblique struts.

[9] The fin was supported at either end by a cross piece attached to the upper longerons of the fuselage and was braced via four wires running to the triangular horizontal stabilizer.