Skyjack is a verb that means to hijack an airplane or other aircraft while in flight. Some antonyms for skyjack could include terms such as "land," "ground," "dismount," or "land safely." These words describe the safe and legal way to exit an aircraft, in contrast to the dangerous and illegal act of hijacking. Other antonyms might include "release," "free," "unleash," or "liberate," which suggest a positive action of letting go of something, rather than seizing or taking control of it.
In general, antonyms for skyjack tend to emphasize the importance of safety, compliance with rules and laws, and valuing the lives and well-being of those aboard an aircraft.