When you download the latest version of vim-airline as .zip and unzip it to a temporary directory, you get a vim-airline-master directory in the temp directory.
Inside vim-airline-master you'll find autoload
, doc
and plugin
directories.
You should either copy these three directories to your ~/.vim/
if they don't yet exist (don't overwrite existing directories with same names!)
or
copy the contents of the aforementioned three directories to existing directories under ~/.vim/