Twins are a totally different animal.
When they started flying across the Atlantic they had to choose a route that took them near to alternates in Iceland and Greenland and Labrador, but with more experience of engine failures, or more properly, lack of failures, then the distance from a suitable alternate was gradually increased,statistics again not logistics.
The same philosophy must apply over the hostile territory of Afghanistan and the like, and I regret that I have no knowledge of the rules on that route - over to someone else.