The plane was quite clearly not taking off from Belgorod. Like I said, Sushko is entirely unreliable and does zero vetting of his “sources.” His translations are notoriously poor.
The flight was entering Belgorod, which follows typical Russian POW exchange procedure according to the NYT. An IL-76 is used to deliver POWs to a nearby city, and they are then shuttled by bus to the border.
But also, if Ukrainian radars can’t tell the difference between a fucking IL-76 and a Su-34 or cruise missile, what the fuck man. Their radar signature isn’t even in the same order of magnitude.