Who is jamming airplanes’ GPS in the Baltic?

.ON APRIL 29TH Finnair, Finland’s national airline, stated that it will put on hold tours to the far eastern Estonian city of Tartu for a month. Last week 2 airplanes were actually forced to turn around after their general practitioner signs were actually interrupted. Family doctor jamming has increased dramatically in the Baltic location over recent pair of years.

Who is behind it as well as how dangerous could it be?