An essential fact to bear in mind in relation to UFOs is that they are etheric in nature. They are etheric-physical, not dense-physical. What we see is the result of their ability to lower the vibrational rate of themselves, or their vehicles, temporarily, to a level where we can see them and know them. The phenomenon of their disappearing is the shift of their vibrational rate up again. This is something which the Masters, too, can do. Those who have control over matter can do this.