Lawyer here
What an interesting case. My research has not found anything like it in the English legal system involving an aviation scenario. Kidnapping in English law was defined in a 1984 House of Lords decision as "an attack on, and infringement of, the personal liberty of an individual." Their Lordships said it consists of four ingredients "1. the taking or carrying away of one person by another, 2. by force or fraud, 3. without the consent of the person so taken or carried away and 4. without lawful excuse." If there is no force or fraud when the individual is deprived of his liberty then the criminal offence is false imprisonment and this offence can be committed both intentionally and recklessly. The latter concept should be understood as a situation where the defendant knew he was taking an unjustifiable risk of taking away someone's liberty without their consent and of course without lawful excuse.