| 1 | Cause it is an altitude of 5000 meters from the ice crystals appear in the volume constitute a stratus . | |
| 2 | When cirrostratus clouds are disturbed by planes or strong winds, the droplets can freeze instantly or evaporate, the latter of which will form the hole. | |
| 3 | These occur in cirrus or cirrostratus clouds, which are often composed of ice crystals and super-cooled water droplets - water that is below freezing temperature, but still in liquid form. |