Controversial post. When you know you have a huge notice period to serve and a new employer who can't wait, make sure you have a good excuse for getting out early before you even write that resignation notice. This excuse should not give your current employer the opportunity to even contemplate.
Do what needs to be done. Lookafter yourself. Thats my moto and it has worked for me. Loyalty in aviation is a one way street. Those of you who haven't seen more than 3 of your past employers go bust of course will never understand.