The FBI has released a notice on media claims about aircraft hacking. You can see the document here (among other places). Thanks very much to Nicholas Larrieu for the pointer to this document. The notice asks for assistance in identifying potential incidents and vigilance in preventing such events. It also says:
"The FBI and TSA are currently analyzing claims in recent media reports which included statements that critical in-flight networks on commercial aircraft may be vulnerable to remote intrusion. At this time, the FBI and TSA have no information to support these claims but continue to leverage public and private sector partnerships to evaluate potential threats posed by intrusions into a commercial aircraft’s secure networks. The FBI and TSA also continuously monitor and analyze reporting on cyber and technical threats to proactively deter individuals from using remote intrusions to disrupt any portion of the aviation sector, including its business networks, critical navigation and air traffic control signals, and the onboard networks of commercial aircraft."