History of the P-40 Tomahawk-- Part 1: 3rd Most Produced American Fighter

From Collins Foundation World War II Planes page.

They were built by the Curtiss-Wright Corporation and were single-seat, all-metal fighter and ground attack aircraft that first flew in 1938.  A total of 13,738 were built between 1939 and 1944, making the aircraft the third most-produces American fighter after the P-51 and P-47.

The P-40 design was a modification of the previous Curtiss P-36 Hawk.  This new design reduced development time and enabled rapid entry into production and operational service.

--GreGen