"hijacked" malaysia confirms, page-210

The pilot would not have known the contents of the cargo bay until it was to late so theft is unlikly, preparation for this has been done over a year since he bought the flight simulator, he would have needed a long time on the simulator to practise the low level flying techniques.
Plus the pilot in terms of wealth was doing alright,his house and the price of the simulator was more than his wage could afford unless he had another form of income or inheritance to justify the cost of the simulator.