Another night, another low-flying triangular UFO. These have been seen in the US at least since the 1970s, so they are unlikely to be spy planes or drones. But what are they? In his book the Grays, Whitley Strieber has a description of a fascinating aircraft called the TR, which is a spy plane. It is actually a blimp, created and deployed back in the seventies. So, is it real? We asked him and got this response: "Fiction, but it shouldn't be. It's a good idea for a close-approach surveillance aircraft and it could be built, but not until battery technology produces lightweight, high power batteries that are the craft's motive power. It's probably 20 years out." Unless, of course, that technology exists somewhere behind the wall of secrecy.