this article discusses further. It appears, possibly, a chance exists that the hacker in question could transmit false data to ACARS and thereby cause the plane's crew to respond to the false info. But I don't see how physical (virtual) control could be taken of the plane. I don't see any mention of that.
Researcher hacks aircraft controls with Android smartphone ? The Register
Teso was also able to use flaws in ACARS to insert code into a virtual aircraft's Flight Management System. By running the code between the aircraft's computer unit and the pilot's display he was able to take control of what the aircrew would be seeing in the cockpit and change the direction, altitude, and speed of the compromised craft.
He admitted that some of this was moot, given that the human pilot could always override the automatic systems, but the software could be used to make cockpit displays go haywire or control other functions, like deploying oxygen masks or lights.
the hackers presentation slides
http://conference.hitb.org/hitbsecco...o%20Series.pdf