May be it has been discussed before ... but a thought has been on my mind.
Why would UFOs meet only "leading nations"?
Why would UFO meet only "specific agencies in those countries"?
We say lets leave some tribes untouched like in Amazon basin n talk about their preservation n not polluting them with modern way of life, would they think of us as primitive and do the same for us? (assuming they are not hostile)
Thinking all this, many prior WWII UFO sightings like in old paintings etc could be anything from a sky phenomenon to asteroid or comets.
During WWII Nazi with their Foo Fighters and Anti-Gravity experiments and V2 rocket work etc were way ahead than other nations. Then WWII ended and all the allied nations took these scientist gave them new country in return for their mind n work. Post WWII suddenly space race went on, and UFO sighting started happening.
Most of these scientists were taken to covert bases as they didn't want their countrymen to know about how they are sheltering "war criminals". Thus they were in very secure bases with infinite amounts of money carrying out the "out of world" experiments with anti-gravity, rockets n so on.
Most of the products of their works like b2 bomber etc are in shape of arcs, and not in shape of conventional airplane designs. Some of the finding made public and rest are still experimented or used today for military or spying purpose over other nations.
May be thats why when a country conducted earlier Nuclear tests, or there were some wars those places had UFO sightings. When ever there were natural disasters there were UFO sightings. May be most of the catastrophic events in recent past were man-made and were due to this new science which most countries are tinkering with.
Now what about Mexico or South American countries who werent part of WWII. Most of these countries had Nazi presence or some people working. These were also looked upon as Safe Haven and may be that time these countries gave fleeing scientists visa for their science.
Thus may be more than 99% unexplained sightings of UFO's are nothing more than Nazi science used by nations which present day man is not aware off.
Only flaw in my thought is how does this explains Alien Abductions?
However i truly feel if there is a race traveling across universe they wont go for some nations, some nations some people to talk to.