Tad off-thread here, but from the financial reporting angle there is a difference if the unpaid leave is voluntary or if there is some undertaking to pay it back in the future.
If the former, both the cash position and financial results are improved immediately by the one-off reduction in operating costs.
If the latter, the cash position improves, but there is no improvement in the financial results as the obligation to pay all the sums out later still has to be booked against current earnings.
So put two and two together and what are we left with???
BA is running out of CASH!