First flown in 1923, the OL was a high-performance amphibian with a large single hull and stabilizing floats fitted underneath each lower wing.

The hull was built of Duralumin on a wooden frame, with five watertight compartments connected through a selector switch to a bilge pump in the rear cockpit.

[1] The United States Army Air Corps ordered four prototypes as the XCOA-1, powered by a 400-hp Liberty V-1650-1 engine mounted inverted for clearance of the three-bladed variable-pitch steel propeller.

Oil from a tank in the fuselage was cooled by passing through a spiral copper tube exposed to the slipstream on top of the cowling.

The Loening OA-1A "San Francisco" is on display at the Steven F. Udvar-Hazy Center of the National Air and Space Museum in Chantilly, Virginia.