One common denominator with many sightings are electrical and electronic malfunctions. It has been speculated that UFOs use a tremendous amount of electricity to go about their business. Part of what makes them so interesting is their movement. They can stop on a dime and accelerate at hypersonic velocities in an instant which begs the question, what type of propulsion are they actually using? One possibility is a Magnetohydrodynamic Drive and you can learn more about it HERE.