The French parasol wing one- or two-seat scout aircraft known as the Morane-Saulnier L, Morane-Saulnier Type L, or formally MoS-3 served in the First World War. When the Type L was equipped with a single machine gun that fired through the arc of the propeller, which was shielded by armored deflector wedges, it became one of the first successful fighter aircraft.

The Type L was quickly rendered obsolete as a result of the arms race in fighter development that resulted from its immediate effectiveness in this role. The Type L originally had wing warping for lateral control, but a later model called the Type LA had ailerons installed.

At the start of the war, the French Aviation Militaire ordered a sizable quantity of the Type L from Morane-Saulnier. There was roughly 600 Type Ls manufactured in all, and they were used by the Royal Flying Corps, Royal Naval Air Service, and Imperial Russian Air Service in addition to the French Air Force.

Pfalz Flugzeugwerke also produced the type in Germany under license as the unarmed A.I. and A.II scouts (with 80 HP and 100 HP Oberursel engines, respectively). For Bavarian air service, about 60 were constructed. A handful of them was later transformed into E.III fighters. A single German Spandau LMG 08 machine gun was installed on a few Type Ls that Germany had managed to acquire. Many people mistake these captured and modified planes for Pfalz E.IIIs.