IPA: /ˈskaɪˌdʒækər/
KK: /ˈskaɪˌdʒækər/
A person who takes control of an aircraft by force, often to demand something or make a political statement.
The skyjacker threatened the passengers to make his demands known.
Skyjacker → It is formed from "sky" (from Old Norse *ský*, meaning cloud or sky) and "jacker" (from the verb "to jack", meaning to seize or take). The word "skyjacker" refers to someone who seizes control of an aircraft in the sky.
Think of someone who 'seizes' ('jacker') something in the 'sky' — that's why a skyjacker is someone who takes control of an aircraft.