The small airplanes are Antonov An-2 1000 HP biplanes (liaison, transport, courrier, ag spray you name it!).
You have also a large bunch of them at nearby Sondok airfield (7 km SW Yonpo, much more recent), along with some Li-2 (this at least I assume them to be; they are russian copies of C-47) slowly and forlornly disintegrating...
