... but some people claim that UFO's are actually aircraft built by the "shadowy types". :furtive:

This is the most credible explanation to me.  Many UFO's have turned out to be military aircraft that later became declassified.  

I remember the story about a spy plane that flew at very high altitudes, at very high speeds over the Soviet Union.

People asked about it, the US government denied the plane's existence...

Then the Soviets shot the plane down and the pilot was taken prisoner, and the US military was all  :scared2:

I can understand keeping the plane's existence secret, due to cold war spooks, but nowadays...

We're still seeing these things.  Aircraft we can't ID.  So what's gonna get shot down next?

EDITED the next day to add:

There's also the very real possibility of demonic involvement.  

This first cult is clearly under demonic influence.  Notice how this guy calls himself "Prophet Yahweh" and claims he can summon UFO's because of some "secret" he found, reading the Old Testament:



This second cult are called the Raelians, they were exposed as a sex cult back in 2005.  They are the same group that claims to have engineered the first human clone.

They claim their religion was started when their leader Rael met an alien in the late 70's named "Yahweh". (sound familiar?)  In other words, they are insane!  They do however still operate and they run a company called Clonaid, claiming they recieved technology from aliens to expirement with humans.  They even have their own channel on YouTube, though this video is not from their channel:



This is weird though:  The Raelians' symbol looks like a mix of a Star of David, and a Swastika.  If you pause the clip at 1:17 you can see the symbol on one of their shirts.

As far as I know, these two cults are unrelated, but both seem just too demonic.

The SSPX has an article somewhere on its site on this. Yes, demons and the military. Sometimes they are one and the same though the higher you go in the military. Also, don't you know the truth behind NASA and Jack Parsons??