I think
Bolty may be correct. An employee can not be "bonded" to a job and financially penalised for leaving within the bond period.
It is my understand the "endorsement bond" always was a
financial bond or guarantee (not an employment bond), which is amortised over a pre determined employment period, possibly five years.
The employee may resign within the bond period of employment, but under the financial bond may be required to repay that residual value of the bond, not yet amortised through employment.
Theoretically at least, an employee "working off" a financial bond could be paid less (by the value of the bond amortisation) than the employee who pays or brings his endorsement to the job. There are also tax implications.
I don't work for the airlines but it will be very interesting to see what occurs if endorsement bonds are introduced, in lieu of paid endorsements. Either way, I suspect the airlines won't be losing.
Just my 2 cents worth!