Being bonded isn't such a big deal or a major problem. I have sympathy with an airline as a business needing to get value for money on what they spend within the business. Of course, by investing an amount of money in the pilot to operate their aircraft, they'd need to see a return. I have no problem with 3/5 year bonds when you're talking about an investment of between £10,000 and £20,000.
I do however agree with Bruce Wayne about having to accept a reduced salary as well. This is unreasonable and is not fair at all.