What cloud forms above 6000?

Clouds that typically form above 6,000 meters (about 20,000 feet) are primarily cirrus clouds. These clouds are composed of ice crystals due to the cold temperatures at such altitudes. They often appear wispy and thin, indicating fair weather, but can also signal changes in the weather. Other high-altitude clouds, such as cirrostratus and cirrocumulus, may also form above this elevation.