A 20-knot headwind or tailwind for a gliding 747 makes for a rounding error, but for an engine-out single it can mean the difference between an on-airport landing and an off-airport tragedy. Glider pilots have charts and techniques for speed and loading to maximize their performance, including adjustments for wind. They call it Speed to Fly; for X headwind increase the indicated glide speed to Y for a new rate of descent of Z.