<p>According to the note at the bottom of <a href="http://www.adobe.com/go/kb403919">this Adobe KnowledgeBase page</a>, there is a bug in Flex Builder 3 when you create a new Air application, it fails to insert the correct Air version into the application descriptor file (&lt;app name&gt;-app.xml).</p><p>You will need to try changing the namespace to either xmlns="http://ns.adobe.com/air/application/1.0" or xmlns="http://ns.adobe.com/air/application/1.1" or xmlns="http://ns.adobe.com/air/application/1.5" depending on which version of the runtime you have installed on your system.</p><p>It was very frustrating for me as I received copies of the files we were using in the Adobe MAX 'Air Boot Camp' sessions, and none of them were working for me on my laptop - while they worked just fine in the lab.</p><p>This is because the files were set to the 1.1 namespace, and I only had Air 1.0 on my laptop. Editing the descriptor namespace to '1.0' allowed me to run the files fine - but naturally I wanted to update to the latest version of Air, so now I can change them to the '1.5' namespace.</p> <br/> <a href="http://www.adobe.com/go/kb403919">http://www.adobe.com/go/kb403919</a> 1 2008-12-07T10:43:48+00:00 16 false true 2008-12-07T11:09:47+00:00 If adl quits on you when you try to run an Adobe Air application from the Flex Builder 3 IDE, you will need to edit your application descriptor file. 2008-12-07T11:09:47+00:00 true 1