Bonding arrangements do differ though. Having to pay something if you leave before 2 or 3 years is fair as the company will have bourne the cost of a new employee. This training burden could be large for a direct entry or fast tracked captain for instance. Initial rating then extra conversion training and additional line training sectors.
what is not so fair is being held for the three years and also having to pay all the money back.
some companies will give you half of the bond back if you stay a certain period of time. So the overall cost is manageable.