The large cargo planes did not land at the field. Instead they slowly flew at extremely low altitude and released the vehicle from the aft cargo hatch as it passed over the gently inclined runway.
The airfield concept was abandoned after the war. The increasing frequency of ion storms and GDI's orbital weapons and surveillance assets induced Nod to adopt GDI's just-in-time system with war factories in the field.
In Command & Conquer: Tiberian Dawn, the cargo plane's flight path is always from the left side to the right side of the screen. Interestingly enough, the plane cannot be shot down or intercepted in any way which is most likely for balance because it would be unfair if Nod's vehicle supply lines could be cut off while GDI's cannot since their vehicles emerge from a weapons factory instead of being airlifted.