It is estimated that over 11,000 Russian MIG-21 'Fishbed' jet fighters have been produced since the first prototype flew in 1955, making it the most common jet-powered military aircraft ever, and the military aircraft produced in the greatest numbers in the post-WWII era. The aircraft has been produced in over 30 different variants and has seen service with around 50 air forces around the world. While the Russian MiG 21 Fishbed is the most widely produced jet fighter in the world (around 11,000), the US F-16 Fighting Falcon is the most widely produced western fighter. The US Air Force itself has around 1,348 F-16s more than 4000 F-16s have been sold worldwide to 24 different nations in over 110 different versions.