These are CIRRUS clouds. They also are 5000-14000 meters in the air. They're made up of ice crystals that get caught in high winds speeds 100 or above. Even though they are clouds, none of the ice ever reaches the ground.
Credits:
Created with images by macayran - "sunset sea of clouds clouds" • judygva (back in town and trying to catch up) - "Clouds: Stratus, Cirrocumulus?, Occoquan Bay National Wildlife Refuge, Woodbridge, Virginia, October 31, 2014" • brownpau - "Nimbostratus Clouds Over Georgetown" • dimitrisvetsikas1969 - "clouds cumulus weather" • Hans - "cloud cumulus clouds cumulus" • Alexas_Fotos - "cumulus clouds sky white" • dsearls - "2013_12_20_lax-iah-iad_42c" • Sangre-La.com - "jc1346.JPG" • Yuya Tamai - "Cirrocumulus cloud" • nachans - "098" • Nicholas_T - "Glints" • debs-eye - "Cirrus"