According to his mother the teen boarded the flight in his quest for a asylum in Germany. Apparently his only option to do so was to acquire a lost/stolen passport to make his escape.
One of the two men who boarded Malaysia Airlines Flight MH370 with a stolen passport was identified as a 19-year-old Iranian with no known terrorist connections, authorities said at a press conference today.
http://abcnews.go.com/...
At least speculation about the intent of one passenger can cease.