This looks like a coordinated attack to me. Just think about it. If GPS spoofing can be used to manipulate a UAV into landing in hostile territory, how hard would it be to manipulate a commercial ship’s course into ramming a US Navy vessel?
A UAV doesn't have a pilot. It is unmanned, which means it is piloted through external controls by someone sitting at a computer. It would seem that this sort of device would be easier to hack than anything else the military uses.