Can Ukraine restore its pre-war borders? Is Russia testing NATO with aerial incursions in Europe? EU to develop'drone wall' amid regional airspace violations European Union defence ministers have agreed to develop a "drone wall" along their borders with Russia and Ukraine to detect, track and intercept violations of their airspace, according to the bloc's defence chief. Friday's announcement comes after rogue drones entered Polish airspace on September 10, rattling eastern EU members. Although Danish authorities have not concluded their investigations, Frederiksen stressed that Russia was currently the primary threat to European security. The Kremlin has denied any involvement in the drone incidents in Poland and Denmark.