In 1933, New Zealander Lowell Yerex, who had flown reconnaissance flights in his Stinson Detroiter for forces loyal to Honduran President-elect Tiburcio Carías Andino in a civil war in December 1931, and subsequently founded the South American airline consortium TACA, was tasked with buying trainers and counter-insurgency aircraft for the Escuela Nacional de Aviación or National Aviation School, which was later to form the core of the Honduran Air Force.

[1][2] Hall's design, the Model O, was a parasol wing monoplane which used the wings and tail surfaces of the Stinson SR Reliant four-seat private aircraft, combining them with a new fuselage seating the crew of two in tandem in open cockpits (the Model O was the first and only Stinson aircraft to have open cockpits).

[3][4] Honduras purchased three Model Os, taking delivery in December 1933, when they formed the initial equipment of the Escuela Nacional de Aviación, with Honduran serial numbers 1–3.

[1] Following the Japanese attack on Pearl Harbor in December 1941, Honduras's Model Os were used to carry out patrols along the coast of the still-neutral country.

With the Spanish Civil War raging, an attempt was made in 1938 by Republican Spain to purchase 100 Model Os, with President Franklin D. Roosevelt's brother-in-law Hall Roosevelt acting as negotiator for the Spanish, but the American arms embargo stopped the deal.