Kingofkabul,
They'd be daft not use use the pretax salary deductions. The tax break the cadets get from this means the pay doesn't need to be high enough to fund the taxes and both the company and the cadet get to save 11% for National Insurance contributions on that segment of salary. The company also gets to reclaim the VAT, so the training bill is significantly lower than it otherwise could be, though the VAT reclamation is not dependent on using a pre-tax salary deduction for cadet repayments.
What is strange about this is that Flybe use post tax salary deductions on their own schemes, but if TC owns these cadets, they can do it their way.