It's not really an turn over as allot of them are new positions, allot of growth within in the next 3 years at NZ.
They're not doing all their hiring for the next three years now.
Yes, without a doubt some of the positions this year are due to the expansion you outline but turnover is a lot higher than it has ever been historically. One the other day said she was the only one left off her course from two years ago. Others had all left (some voluntarily, some under direction).
The company is well aware of this and seems happy enough (it's what they wanted). Get them in on reduced terms and conditions to what has previously been on offer. Have them do the job for a while then off they go to do other things. Don't blot your copybook and these guys/gals are making ISM (the lead FA) after 12 months.