A parallel line of cirrus cloud that was so large it covered the whole length of the sky from horizon to horizon. In fact, the cloud photo on the first thumbnail was taken from the opposite horizon of the sky. Furthermore, the photographed cloud was even visible through satellite imagery taken at that time (around 19:45 CEST) as per second thumbnail in which this high-level cloud seemed to be of several kilometers in length, much larger than Malta itself. The strong jet stream could be linked due to tight pressure gradient over the area at 500mb height as per 4th thumbnail. Such cloud forms when water vapour at high altitude become ice crystals that as per 3rd thumbnail was moved by an overhead strong jet stream of around 200kmh. Its tendrils which is clearly visible in the cloud photo on the first thumbnail is actually due to precipitation from the cloud itself hence is actually a precipitation cloud. However, due to its considerable altitude and the very strong upper-level winds that cause its formation in the first place, the precipitating snow evaporates well before reaching the ground.