[schreiaj]

Ability to divert in an emergency?

[perilunar]

Absolutely. It's a map of closest airport for any location on earth.

You could do different versions of this for different classes of plane (e.g. select a minimum runway length).

[mikeash]

This has a big influence on which routes a plane can fly. You can’t be more than a certain distance from a usable airport at any time during the flight to mitigate the risk of engine failure resulting in an off-airport landing/crash. See: https://en.m.wikipedia.org/wiki/ETOPS

[isostatic]

And diversion airports of course vary with things like weather