In USSR there were about 20 big aircraft factories. We didn't build underground factories, but moved many industries to the East.
Before the WW2 main aircraft factories were in Moscow, Leningrad (now Saint-Petersburg), Kharkov, Gorky (now Nizny Novgorod), Saratov, Voronezh, Kazan, Novosibirsk, Komsomolsk-na-Amure (far east), motor factories in Moscow, Perm, Omsk, Kharkov.
During the war Kharkov plant was lost because of occupation, many Moscow and Leningrad factories moved to other cities: Kazan, Novosibirsk, Tashkent, Kuibyshev (now Samara). Usually 2-3 plants "consolidated" into one. For example, 124-th plant in Kazan "assimilated" two factories: one moved from Moscow, other from Leningrad.
During the war USSR produced about 120000 planes, it's second achievement after USA. For example, only 292th plant in Saratov (new one, established just before the WW2) produced in 1942 3474 Jak-1 fighters and in 1943 2720 (the reducing is because it was transferred to Jak-9 production). It means about 10 fighters per day.
We used conveyor and other mass-production methods.
And in the picture he is Novosibirsk plant in 1943 (153th plant, later named after Chkalov). Each hour the new fighter Jak-7 flew from this factory.