I have heard & seen very similar from my mom's house in Las Vegas,before it was all built up like it is now. We suspected they were some type of military air crafts flying near the mountains. We may never know,but used to enjoy the light shows. We often saw several at a time,and they changed direction like no known aircraft can that I'm aware of. They would hang around sometimes,and then would take off, change directions at extreme speeds. We looked into it & sometimes we would see UFO reports in local rag papers,but stillsuspect it was something military,even though the papers said they contacted the base at Nellis, yet were told it was not theirs & the base suggested it might be a helicopter. These were certainly not helicopters...they were far too big & far too fast to be.

If it made a "whirring sound" there is the possibility it was not a "genuine extraterrestial vehicle" because the EVIL CONSPIRACY may be trying to "imitate" flying saucers and there are "crude imitations" that are based on "fans" which lift entire vehicles into the air, kind of like drones, only they have a "saucer shape" to make people believe they are "from out of this world" when in reality they are not, NO, I DO NOT THINK YOU ARE CRAZY, but you may have witnessed a "fake UFO" from a "wicked conspiracy" that wants to drive people crazy, by creating these "whirring UFOS" so that they can "discredit" the UFO phenomena and claim we are "cattle slaughterers" which as I stated I do not know any "ET" civilization that would have any incentive to "slaughter cattle" in order to "use for research" or other purposes, we "do prosecute" such events, therfore if you can "shoot a cattle rustler down" that would be "very helpful" indeed, but be careful you do not shoot at any "innocent bystanders" or utility helicopters, make sure they were actually rustling your cattle, before you shoot them! I think you might even be "covered by federal law" if they are over your property, after all they are "intruders" and "honest aliens" from outer space will not "violate your property rights" I can assure you of that, they would "purchase the cattle" before they used it for any "scientific investigation" etc, but then again the US government has so many "dark operations" it is hard to believe!