According to the latest news, over dozens countries have already built their own military drones. Every country will have military drones within a decade. Not to mention that some of the countries already have the technologies will be exporting. For example, Saudi Arabia had ordered drones from China. Eventually drones with missiles attached will be in the hands of everyone. Drones are small which means it's harder to detect them than a standard manned aircraft. Many drones can be launched anywhere without a runway, it means it's even harder to detect them and even if detected, it's going to be a very short notice. Do you think it will be a terrifying scenario? If these weapons fall into the wrong hands, lets say some terrorists/extremists/assassins, they can be extremely dangerous. Someone can launch it from within a city to strike a building or a person inside the city. The drones can fly between buildings since they are so small. Military jets patrols will have little time to react if any at all.