Orb UFO is filmed over Zagreb Croatia

This video posted on YouTube shows what looks like a white orb flying over Zagreb in Croatia.

At first the orb looks like it could easily be a reflection from inside the room, but when the light is switched off to get a better look you can see it is outside.

The guys filming the UFO debate whether it is an airplane or not, until it makes a manoeuvre that would be impossible for any conventional aircraft would make.

What do you think?