Extremely. The hijack theory is silly. It’s just way too easy to buy a plane in this world. You hijack a plane to use it NOW, if it’s part of a long term plan buy it from one of the many many boneyards (long term storage) facilities scattered around the world.
What if you hijack a plane and repaint it to make it look like someone else’s aircraft when you finally use it to do whatever you’re planning? That way someone else gets blamed for what happened.
For instance, repaint a 777 with American Airlines livery and then slam the thing into the Kaaba in Mecca. No matter what denials the US makes the entire Muslim world will be forever enraged at America because in their minds an American Airlines plane destroyed their holy site.
While this is certainly fanciful I would not put it past Putin, a KGB agent, to run a ‘maskirovka’ like this because that’s the kind of thing that the KGB excelled (excels?) at.