Returning to Greece from Novosibirsk, Russia. A shot from the airplane. From top to bottom: Cirrus clouds, airplane wing, Cumulus clouds. Cirrus are high level clouds. Cumulus on the contrary are low level. The difference can be seen on this picture. More info about cloud types here.
FinePix E550, 04/08/2008 14:29, Shutter Speed 1/550, Aperture Value 5.0, ISO 80