So it could be a couple of years at least to replace the crew then?
Yes according to those figures I guess so, but that is no problem - who says you have to sack everyone all in one go? Hypothetically, you could give the choice of a new contract to sign or a notice of dismissal, and set the dates as you like. You do this to a handful of illegal strikers at a time at whatever your training rate is. I can't see this scenario happening though, because the company is a far fairer employer than the militants give them credit.