I have discovered that most AIR ‘Build Project’ errors are related to a malformed yourapp-app.xml file. Such is the case with the 105 Error of the FileType variety.
I created an AIR app that would support my own File Type extension (mime type). In the fileType’s ‘name’ node, I put ‘My Custom App’. Seemed reasonable since the template comments stated ‘The name that the system displays for the registered file type. Required.‘
Turns out that the ‘name’ needs to be space-free and separated by dots:
In the case of the 104 Error, I uncommented the ‘contentType’ and entered the mime type (which was text/xml in my case).
Hope this saves someone some time and aggravation.