Perhaps the practicioners know about their own legislation and therefore relevant treatment of the Cadets' tax affairs?
"For cadet entry First Officers resident in the UK on entry into the airline, we have been advised by the Inland Revenue that course training cost repayment may be from gross salary i.e. before tax. For cadets resident outside of the UK during the repayment period the deductions will be made from net salary i.e. after tax."