Developing new rich internet application

We are about to start developing a RWA(rich web application) for advanced data management on our web server using PHP/MYSQL/JavaScript. I just came across AIR, which as well as I can tell, allows you to run Flash applications on your desktop instead of in the browser. Do I have this right or am I way off base?

Are there any other options than AIR?

Data security is paramount. We need to be sure that any data stored locally can be encrypted and that the communications between the user and the server can be done so via SSL.

Speed to use is also very important, it can't lag like some flash apps.

Also we are web developers and our guys well versed with PHP/MYSQL/Javascript - can these languages be used with AIR or something similar or do we have to develop the full application in Flash?

This is more so a fact fin开发者_如何学Pythonding mission to see if the 'RIA' buzz can apply to our situation. Thank you!

Silverlight & WPF are some other options. Here's a page that compares these with Flash & AIR.