There's no doubt that the Biefeld-Brown effect is real and can be used to generate thrust in an atmosphere. What is more doubtful is that we have the technology today to use this effect to perform maneuvers that are commonly attributed to UFOs. These devices do not generate large amounts of thrust, in fact as far as I can tell they can barely even hover.

As a side note, people tend to look to these kinds of technologies for explanations for UFO propulsion feats because they seem high-tech, but also because they are *quiet*. Really we could build craft today that perform some really amazing maneuvers, but they are generally loud, so people rule them out as UFO engines because people who claim to have seen UFOs perform these maneuvers emphasize that they do it quietly. But the reason this type of propulsion device is so quiet is precisely because it generates very little thrust. I hate to use a trite oversimplification, but these things generate thrust by pushing on the air around them, and they can only generate more thrust by pushing harder, or pushing more air. Pushing more air means getting bigger and adding weight, and pushing harder on the air means making more sound. Sound waves are just pressure waves, and you can't have air moving fast through other air without making lots of noise (just look at how loud rocket engines are). It just doesn't add up as far as I can tell: to perform these types of maneuvers you need lots of thrust, and to get lots of thrust with an engine that generates it by changing the momentum of the air molecules in or around it you will generate lots of sound.

You're looking in the wrong area. Figure out how they suppress the sound their engine creates, or how they generate thrust without changing the momentum of the molecules around them. And before you patent it be sure to tell me so that I can beat you to the market and make millions.