The "Airacobra's" unique
design placed the engine behind the pilot. It used
an Allison V-1710-85 12 cylinder, liquid-cooled,
in-line engine with
a single-stage rated at 1,200 horsepower.
The lack of a supercharger left the Airacobra under-powered at higher altitudes,
yet it was quite effective in ground attacks.
Nearly half of the 10,000 P-39's built were exported to the Soviet Union where
the pilots were intrigued by its toughness and durability.