Why do elephants flap their ears so much?

The reason why dogs and birds pant through their mouths and elephants flap their large ears, is to control (reduce) their temperature.

Some animals can sweat through their skins and cool themselves as this sweat evaporates from their skin.

However, dogs, birds and elephants (and perhaps some other animals) can not sweat so they either evaporate water in their mouths or pump blood into their 'radiator' sized ears to cool themselves.