Here’s an uncomfortable image to keep in mind during your next flight: A rogue hacker who can redirect planes at will with the touch of an Android phone’s screen.

That’s the frightening scenario laid out by Hugo Teso, a security researcher for the German IT consultancy N.Runs, in a presentation at the Hack In The Box security conference in Amsterdam Wednesday. By hijacking a protocol used to send data to commercial aircraft and exploiting bugs in flight management software built by companies including Honeywell, Thales and Rockwell Collins, Teso told the crowd that he could send radio signals to planes that would cause them to execute arbitrary commands such as changes in direction, altitude, speed, and the pilots’ displays.