Court documents filed by the FBI suggest that a U.S.-based hacker gained access to several flights' computer systems, and even briefly changed the path of one flight. Chris Roberts, a US security researcher, “stated that he thereby caused one of the airplane engines to climb resulting in a lateral or sideways movement of the plane during one of these flights,” according to FBI agent Mark Hurley. Over the past four years he also accessed the in-flight entertainment systems of around 20 flights. The hacks were not authorized by authorities.