Originally Posted by RBower

I doubt they use any formula, just seat of the pants type planning. Headwind? Full blast. Tailwind, .76 sounds good! More detailed, efficient planning is out the scope of this company.

If you want to maximize mileage use the specific range readout in the performance page. But I know of no rules of thumb and we don't have any wind trade off data. Remember though the idea is to fly the airplane at minimum cost, not minimum fuel. Time costs money too.