I ran into a user on multiplayer callsign "Jack" flying a Twin Otter. He wanted me to check out his hometown airport, so I did. When I got there in the UFO, it was snowing. Jack showed up and took me for a flight.
Edit: There isn't anything wrong with the sound, except the UFO sound is based on airspeed in like thousands of mph. I changed my UFO sound to be dependent on the throttle setting.
I know it was at Niederöblarn Airport (LOGO). I was Jack's wingman so to speak. He navigated, I followed. We started there and ended there. I would guess we just did a big circle around the mountain to the north of the airport.