I've just completed the selection process and it is my (unqualified) opinion that the letter which you have received is the first step in the selection. Should you choose not to follow it up, then clearly you don't get in. On the other hand, following it up on a regular basis (perhaps an updated resume evry 3 to 6 months) could see you being invited.
I had been applying for over 2 years before I got the nod for an interview. Also, having done all of my homework, I don't believe that you will find a better airline in terms of career and human prospects.
