 At the same time that the daylight escort fighter was developed from the SM-2 and SM-9 into the MiG-19 and Mig-19S, work went on in parallel to design and build a radar-equipped all-weather fighter, with the first prototype SM-7/1 flying for the first time on 28 August 1954.This prototype had a similar airframe to the first SM-9, including the conventional fixed horizontal tail, with the second and third SM-7s introducing similar changes to those tested on the SM-9 prototypes, including the slab tail.The all weather fighter entered production as the MiG-19P in 1955.