The government(s) have technology that the public doesn't know about. Long time in developing & back-engineering this. If it were to be brought out & used, most would think that its the aliens.
Also, check out Charles Hall story while he was stationed near Area 51... The U.S. military has built a huge facility to house aliens known as the Tall Whites. The military never briefed the men stationed there as to what they were to encounter. It was used like an experiment on these enlisted men - to see how they would react. These aliens also provided technology to the military.
Also this video... (note: Charles Hall likes to keep his presentation on the light side, adding his sense of humor to it. Notice he mentions that several of the service personnel were scared to death, as a number of them experienced being attacked by these Tall Whites. Makes one wonder, with generals & CIA escorting these aliens into casinos in Las Vegas, what kind of military leaders are running this thing?)