@FreeSpirit1 Because jet fighters can't move as fast or as quick as these things. They are monitoring using other methods. Also studying how they propel themselves.
@Livingwell if they were a threat to America, they would have been shot down weeks ago, I’m sure the great big strong country that can attack countries like Somalia, Sudan, Iraq, Syria, Libya, Lebanon, and soon Iran, can sort a few drones out, it’s quite obvious these drones, come from a military base in America,