Ideal forward speed for max. distance on a charge?

[GadgetGuy]

the maximum flight range is about 14 m/s and corresponds to 50 km/h.
At the optimum cruising speed of "DJI Phantom 3 professional" of about 14 m/s the estimated flight time is 17 minutes and the maximum range is over 14 km away.
long range drone DJI Phantom 3 professional

This is consistent with the results of long distance flyers who have empirically arrived at 31mph as the most efficient speed for maximum distance. Results will change by adding additional weight for external batteries to achieve longer flight times, as well as DJI throttling of speeds when flying downwind in later firmware and app versions, as well as forced Autoland at 10% remaining battery. Good stuff!