The first jet combat aircraft designed and built in Canada was the two-seat Avro CF-100. The project was started in 1946 with the first prototype flown on January 19th, 1950. Ten pre-production Mk.lls were followed by 70 Mk.lll production versions. On October 11, 1952, the prototype of the second operational variant appeared. The Mk.lV first flew with improved avionics and armament, plus more powerful engines. The last version was the Mk.V with a further increase in power. The RCAF accepted a total of 692 CF-100s and further 53 (all MK.V) were sold to Belgium. Officially the speed of CF-100 was limited to Mach 0.82. It was known with some derision as the "Clunk" or the “Lead Sled”. The last CF-100 was retired in 1981.