I fully understand 'global'. You need more than one fleet type, that's a given. Five, even six would work. Ten is insane and a huge drag on the bottom line. (read 10 training events for 1 retirement). Parts? Forget about it.
How do you know there will be 10 training events for every retirement? Do you really think they'll have 8,000 training events per year 10 years from now when 800 guys hit 65?