text: greatly with altitude, the turbojet can tolerate 
  less favorable (or more unfavorable) winds 
  with increased altitude. 
  
  In some cases, large values of wind may 
  cause a significant change in cruise velocity to 
  maintain maximum ground nautical miles per 
  lb. of fuel. As an example of an extreme con- 
  dition, consider an airplane flying into a head- 
  wind which equals the cruise velocity. 
  In this 
  increase in velocity would improve 
  case, ““9 
  range. 
  
  While many different factors can affect the 
  specific endurance, the most important factors 
  at the control of the pilot are the configuration 
  and operating altitude. Of course, for maxi- 
  mum endurance conditions the airplane must 
  be in the clean configuration and operated at 
  the proper aerodynamic conditions. 
  
  To appreciate the changes in optimum speeds 
  
  with various winds, refer to the illustration of 
  figure 2.26. When zero wind conditions exist, 
  a straight line from the origin tangent to the 
  curve of fuel flow versus velocity will 
  locate 
  maximum range conditions. When a head- 
  wind condition exists, the speed for maximum 
  ground range is located by a line tangent drawn 
  from a velocity offset equal to the headwind 
  locate maximum range at 
  velocity. This will 
  some higher velocity and fuel flow. Of course, 
  the range will be less than when at zero wind 
  conditions but the higher velocity and fuel flow 
  will minimize the range loss due to the head- 
  In a similar sense, a tailwind will re- 
  wind. 
  duce the cruise velocity 
  the 
  benefit of the tailwind. 