The Loire 70 was designed to meet a 1932 French Navy requirement for a long-range flying boat for maritime reconnaissance and bombing. The prototype first flew on 28 December 1933. It was an all-metal monoplane, with a heavily braced high wing, with three radial engines mounted above the wing, two as tractors and one as a pusher. The original engines, three 500 hp (373 kW) Gnome et Rhône 9Kbr radials, were not powerful enough and were replaced with 740 hp (552 kW) Gnome-Rhône 9Kfr radials. Seven production aircraft were produced.
The seven production aircraft and the prototype were all delivered to the French Navy, serving with Escadrille E7 at Karouba in Tunisia. During the early days of World War II, the aircraft carried out patrols in the Mediterranean. In an Italian air raid on their base on 12 June 1940, three of the four surviving aircraft were destroyed. It is not known what happened to the last aircraft.