I was there last summer, it is my home city. The museum used to have more stuff exterior than it is nowadays.
All of these things were there since the late 80s at least, according to older people. When I were younger, there were more MIG 21 and MIG 19 and various rocket pods and cannons, but it seems to be removed and replaced by the boutiques. There is a smaller storage nearby, around a army's stadium, where they store those things.