Following the entry of the U.S. into the war it was realized that there was an insufficiency of aviation training facilities, both in the U.S. as well as in France. This condition coincided with the need for additional need for aircraft designed by European manufacturers. This dual need was partially addressed by having both the A.E.F. Air Service and the U.S. Navy have pilots trained in Italy. In exchange, Italy was going to provide aircraft for the American personnel to fly. The result was that the Italians provided training facilities for A.E.F. pilots. These pilots, following training, served both with Italian units or were transferred to the Western Front in France. The U.S. Navy operated at traing facility at Lake Bolsena and operated a naval air station on the Adriatic.

The L.3 was ther final evolution of the Italian copies of the Lohner Austrian flying-boat, the L.1 and L.2, (copied from captured enemy machines) with revised lines, slightl smaller wingspan and 180 hp Isotta Fraschini V.4B engine. The Macchi L.3 was built in relatively small numbers (about 220 examples) only by the Macchi works, but it was the most active seaplane in the Adriatic air war. Production began in october 1916 and the first ones reached the front in early 1917. Used as a bomber and reconnaissance airplane, it flew from the naval air stations of Venice, Ancona, Brindisi and Otranto, facing the Austrian seaplanes of Trieste, Pola and Kumbor.

Compared to the similarly powered FBA type H, the L.3 was considered a much better aircraft, with betetr performances and safer flying qualities. In early 1918, when the Army reconnaissance squadrons were suffering from shortage of airplanes, the L.3 was even used for gun spotting and reconnaissance over land,c arryign Army observers and facing land fighters. Extremely durable, it served until the end of the war. In 1919, a few examples were sent to South America on a good will mission, during which they performed many notable flights.

The Macchi L.3 served with Squadriglie 251a and 252a at venice, 253a at Grado and then Venice, 254a at varano, 255a at Brindisi, 256a at Otranto, 259a at Venice, 263a at Porto Corsini, 265a at Brindisi and the S.Maria di Leuca Flight. Americans flew the Macchi L.3 at the Bolsena Naval Air Station schoool for Naval pilots, and a few examples were still available when the Porto Corsini Naval Air station was established, in the smmer of 1918.