I think several of the UFOs observed are natural objects which behave in a weird manner due to the circumstances.
An old video taken from space showed an object in direction to earth but changed it's course and went fast to the outer space again.
In the video, when one observes the angle of the camera with respect to the object in question, one realizes that the speed of the object trying to enter thru the atmosphere of earth, being rejected and going in a different direction in a faster speed, is nothing but the angle of perception of the event. That actually the object was traveling at the same speed all the time. It was a meteor perhaps, which by approaching earth bounced on the atmosphere and continued its way.
Lets say you observe the object from inside the atmosphere. And from your position you see the object moves slowly or/and even it's stationary at one spot, but actually the object is coming towards you. But, the object is coming in such an angle, lets say 15 grades and at the time of colliding with the atmosphere rather than getting inside it just bounces and goes in a different direction. From your location the object will appear that has changed its direction at a faster speed. The optical illusion caused by distance and motion will make you think the object was going slow first and that changed its speed later.
The colour of the objects in space is also a common optical illusion.
There are several witnesses who have observed similar phenomenon in space, but mostly from far away distances. However, the best reports of closer encounters with objects which belong to heavenly people come from religion, like the Kebra Nagast, when is mentioned the existence of heavenly wagons which travel from place to place at very fast speeds. The story includes people using those wagons or traveling inside them.
And the King asked the people, saying, "When did my son leave you?" And they answered and said unto him, "He left us three days ago. And having loaded their wagons none of them travelled on the ground, but in wagons that were suspended in the air; and they were swifter than the eagles that are in the sky, and all their baggage travelled with them in wagons above the winds...
... And the ambassador of PHARAOH answered and said unto the King, "O King, live for ever! My lord, King PHARAOH, sent me unto thee from ALEXANDRIA. And behold, I will inform thee how I have come. Having set out from ALEXANDRIA I came to KÂHĔRÂ (CAIRO), the city of the King, and on my arrival these men of ETHIOPIA of whom thou speakest arrived there also. They reached there after a passage of three days on the TAKKAZÎ, the river of EGYPT, and they were blowing flutes, and they travelled on wagons like the host of the heavenly beings. And those who saw them said concerning them, 'These, having once been creatures of earth, have become beings of heaven.' Who then is wiser than SOLOMON the King of JUDAH? But he never travelled in this wise in a wagon of the winds. And those who were in the cities and towns were witnesses that, when these men came into the land of EGYPT, our gods and the gods of the King fell down, and were dashed in pieces, and the towers of the idols were likewise broken into fragments. And they asked the priests of the gods, the diviners of EGYPT, the reason why our gods had fallen down, and they said unto us, 'The Tabernacle of the God of ISRAEL, which came down from heaven, is with them, and will abide in their country for ever.' And it was because of this that, when they came into the land of EGYPT, our gods were broken into fragments.
