I think your client misunderstood what AIR is.
I wrote an article about AIR in my blog
here and
here, and to save you time, here is a quick rundown on AIR taken from Adobe's website:
"Adobe AIR was first presented to the public in March 2007 (back then under the name Apollo) and was released as AIR in June of the same year. It is based on the open-source rendering engine called WebKit (the same that is being used by Safari and the iPhone) and supports Flash (ActionScript 3.0),
CSS,
HTML and
JS natively. It enables designers and developers to build rich applications that deploy to the desktop. Adobe AIR applications run across operating systems and are easily delivered using a single installer file. With Adobe AIR, developers can use their existing skills in Flash to build highly engaging, visually rich applications that combine the power of local resources and data with the reach of the web."
For the project you are talking about 'normal' Flash should do it then unless the client wants some sort of desktop app to go with the site?