"As I said earlier, I am not sure it is legal to withhold references of fact (i.e. this guy worked here from date X to date Y etc) with a view to preventing future employment."
that is the case in the UK - not sure about anywhere else - to any potential employer absence of the words "honest", "hardworking" etc etc are a flashing red light anyway
"but I doubt even many of the airlines know what laws applies in these cases! It's all twisted!"
I'm willing to bet that airlines employ lawyers whereas its clear that many people, in their understandable but desperate, rush to become pilots, sign whatever is put in front of them and then start whining 2 years later
It's NOT twisted - you signed up to the deal