That sounds like a good explanation, wiedehopf.
An An-12, UR-CNT, belonging to Ukraine Air Alliance has just gone overhead from Shannon. I heard what sounded like a Dash 8 or suchlike on climbout from Newcastle, logged into FR24 on to see what was departing at this time of night, and it turns out it's an An-12 at 25,000! Let's see if it makes any strange shapes on its way to wherever it's going...