ollie989898
Member
Russian radar is a bit more sophisticated than (and don't rely on) using open source flight tracking websites which require an aircraft's transponder and ground based receivers.
I suspect, that these transponders are left on deliberately, as a show reassurance/confirmation (and political gesturing) to those inside Ukraine that they are not entirely alone; and the west is doing what it can, without risking escalating to a wider and more drastic conflict.
They would need their transponders on to traverse over Europe safely- the skies are loaded with civil aviation of all kinds at the moment.