OK - so should US Vice Presidents travel commercially as well?
When the Prince travels as a representative of the United Kingdom, security considerations as well as the need to move a fairly substantial staff, basically make using personal aircraft the only viable choice.
Until quite recently, the Prince also used to take the controls of those aircraft himself at some point in the flight. I don’t believe he does that anymore, but it’s another reason why he liked travelling the way he does.
Maybe he could just Webex.... if he’s so concerned about the environment