Fleet commonality cost - crew training cost.

[qunow]

Now I have 56 A300/310 and 44 A330/340. But why the crew training cost / month for those 56 A300/310 is only 5.6M, while those A330/340 in fewer quantity would require 6.5M/month for crew training cost?

[MRothschild]

Economies of scale.  When planning fleet groups, it makes sense to have at least 20 in each for the economics to begin to be optimized.  The larger the group, the better.

[Sami]

There is an aircraft size related factor in the cost model which explains most of the difference.