One of the things that emerges from a recent Special Tax Commissioner decision on this is that if contractually the airline arranges to take bond repayments from your salary whilst you serve your notice, then tax is only payable on the reduced amount of your salary. This potentially gives you full tax relief on the repayment depending on how much you owe.
It is therefore worth pilots negotiating with employers that this happens under their contract. The pilot saves tax and the employer pays less NI contributions on the reduced amount to the employee.