A fresco entitled "The Crucifixion" was painted in 1350. It is located above the altar at the Visoki Decani Monestary in Kosovo.

In 1964, “discovered” by art student Alexandar Paunovitch in a 16th-century fresco of the crucifixion of Christ, located on the wall of the Visoki Decani Monastery in Kosovo. The French magazine Spoutnik printed them, and they have been featured in many books and web pages ever since as “spaceships with a crew.”

While a layperson might be completely mystified by these suggestive images, a Medieval art historian would only need to know that they were located in the upper corners of a depiction of Christ’s crucifixion to identify them.

Many crucifixion paintings and mosaics done in the Byzantine style show the same odd “objects” on either side of the cross. They are the Sun and the Moon, often represented with a human face or figure, a common iconographic tradition in the art of the Middle Ages.

James Hall, author of the Dictionary of Subjects & Symbols In Art writes: “The sun and moon, one on each side of the cross, are a regular feature of Medieval crucifixion [paintings]. They survived into the early Renaissance but are seldom seen after the 15th century. Their origin is very ancient. It was the custom to represent the Sun and Moon in images of the pagan sun gods of Persia and Greece, a practice that was carried over into Roman times on coins depicting the emperors.

…[T]he sun is [sometimes represented as] simply a man’s bust with a radiant halo, the moon [as] a woman’s, with the crescent of Diana. Later they are reduced to two plain disks. The moon having a crescent within the circle, may be borne by angels. The sun appears on Christ’s right, the moon on his left.”

The Sun and Moon are depicted as anything from a flat disk to a hollow comet-tailed ball. The figures within vary from a simple face to elaborate depictions of Apollo and Diana in their chariots driving horses or oxen. The Sun and Moon are also featured on crucifixions painted by Dürer, Crivelli, Raphael, and Bramantino.

The two objects in the painting, which could be considered UFO's have people on the inside and some kind of rays coming out of the back of the flying machine.

There are a vast number of paintings, drawings and tapestries around history with some kind of weird elements, leading us to think why the artist painted something like that...

Let's assume and artist get paid to paint Jesus crucifixion, the artist start painting what he knew that supposedly happened during that time. 

Then he will finish the painting with things he know to be everywhere, for example: houses, people on the background, vegetation, sky, clouds, flying birds...

Why paint some kind of flying machine with people on the inside. Are they used to see those flying crafts everyday like you see clouds and birds on the sky? Why paint something like that if that's not part of the everyday life or part of the crucifixion? 

Many Medieval paintings bear a flying object that is seen flying in the sky with radiations coming out of it. ‘Madonna with Saint Giovannino’ is a classic example of such painting.

These flying objects are a proof that UFOs are not sighted only in the recent times, but they have been a regular phenomenon over centuries.