The Adobe AIR platform has introduced the new .air type of install file for their cross-platform offering and while many eager Adobe AIR programmers are offering their custom built .air projects on their websites, most haven’t gone to the effort of setting up the correct MIME type on the server. Of course, this means that in most cases browsers incorrectly deduce that it is a standard ZIP file on offer, causing unnecessary confusion on the part of the user and in its own way perhaps introducing a barrier to the willing adoption of the AIR platform.
A good way to deal with this is to set up your Apache web server to deal with this by setting the appropriate MIME type via your .htaccess file in order to deal with the .air extension. In order to do this, all you need is add the following line to your file:
AddType application/vnd.adobe.air-application-installer-package+zip .air
Upload the file to your server and you should now be good to go! :)