From ABC News:
Several flights across Europe received alleged bomb threats Tuesday that ultimately turned out to be hoaxes but prompted searches, diversions and, in one case, an escort by the Italian Air Force until landing, officials said.
The impacted airlines included Polish airline LOT, Scandinavian Airlines, Wizz Air and Ryanair. No one was injured. A day earlier, a plane headed for Bulgaria was diverted to Hungary after receiving a similar bomb threat while in the air.