[charlesdenault]

What do you mean by a grid? Long-haul direct flights offer many benefits, such as lower drag at cruising altitude, engine efficiency at altitude, etc. [1] Biggest fuel savings are going to come from more efficient engines and weight reduction (composites). 1: https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft

[jlebrech]

you find the optimal distance for a flight and create a mesh out of those flights. and stop lines from crossing.