During the late 1920s, the South American nation of Argentina began building a powerful naval fleet to defend its 2,500-mile (4,000km) coastline and critical navigation lanes - the fleet was named Flota de Mar . This was an era when fleet commanders relied on ship-borne spotter aircraft to 'look' over the horizon (the introduction of radar was still many years away) and in 1927 Argentina's Ministerio de Marina began seeking reconnaissance aircraft for the country's naval air arm, Servicio de Aviación Naval .