The term "skyjacker" refers to someone who forcefully takes over an airplane while it is in flight. However, there are other words that can be used to describe this action. One possible synonym for skyjacker is hijacker, which is a more commonly used term that describes someone who takes control of any type of vehicle or transportation. Another synonym is aeropirater, which is a term that is derived from the words "aero" and "pirate". This term is not as common, but it is sometimes used in literature or media. Finally, the term aircraft thief can also describe someone who takes a plane by force or without permission.