There is a simple experiment you could do without going out and waiting for lake to freeze.
You can use various airlines websites to check a travel time between major cities of the world. Make sure you pick cities from all continents. You can check and write down aircraft flight speed.
Avoid picking short distance flights. There is more influence of start and landing manuvers on flight time there.
Ensure at least 3 connections from each city.
There is a difference of flight time between east and west direction. Even 2h for 10h flight. Just in case, pick only one direction for experiment (other ideas welcome).
Now you have your data.
Now take some stiff wire.
Cut wire into pieces proportional to travel time e.g. 1h equal to 1inch. If you want to be more precise, you can use aircraft speeds and calculate distances to use them instead of hours.
Use glue gun or other way to connect wires.
Make sure you attach a tag to each node to ensure you remember which city is it.
You should be able to keep adding cities and the whole wireframe should remain more or less flat. At the end you can even print a map in a proper scale and check if it fits.