The problem I see with the someone wanted a plane to fly on an ongoing basis is that planes need service at regular intervals. Practically ever single part of an airplane has a serial number and that is going to make things more difficult.
If we are talking about using it as a delivery system, why go to the hassle of stealing a plane full of people?
I still go with it was taken for the hostages or for what they knew.
“I still go with it was taken for the hostages or for what they knew.”
Was there someone(s) with unusually valuable knowledge aboard?