The Speed for Maximum Range Is Not the Speed for Maximum Time Aloft
In a hurry? Skip straight to the numbers.
Open the Fuel Burn Range Calculator →The companion calculator computes still-air range from usable fuel, burn rate, and true airspeed - a clean baseline. Hidden inside it is a question with two different answers: what speed should you fly? If the goal is to travel the farthest, and if the goal is to stay up the longest, the answers are genuinely different speeds, and knowing why is the heart of cruise efficiency.
Two Goals That Pull in Opposite Directions
Range and endurance sound like the same virtue, but they optimize different things.
| Maximum range | Maximum endurance | |
|---|---|---|
| Goal | Cover the most distance per unit of fuel | Stay airborne the longest per unit of fuel |
| Optimizes | Miles per pound of fuel | Minutes per pound of fuel |
| Speed | Faster | Slower |
| Who wants it | A cross-country flight reaching a distant airport | A search or surveillance aircraft loitering over one spot |
It All Lives on the Drag Curve
An aircraft's total drag is the sum of two opposing parts: induced drag (from making lift), which dominates when slow, and parasite drag (from pushing through the air), which dominates when fast. Their sum traces a U-shaped curve against speed. The bottom of that U - minimum total drag - is where the wing is most aerodynamically efficient, and that speed gives maximum endurance for a jet, because minimum drag means minimum thrust means minimum fuel flow to stay up. Maximum range needs something slightly different: the speed where the ratio of speed to fuel flow is best, which lies a bit faster than the minimum-drag point. So the range speed is always somewhat faster than the endurance speed - never the same number.
The Practical Speed Nobody Advertises: Carson Speed
There is a well-known refinement worth knowing. The theoretical best-range speed is efficient but slow, and flying it costs a lot of time for a small fuel saving. Carson speed - sometimes described as "the least wasteful way of wasting fuel" - sits faster than best-range speed and recovers most of the trip time for only a modest fuel penalty. It captures a real-world truth: the mathematically optimal range speed is rarely the one crews actually fly, because time has value too.
Why Wind Changes the Best-Range Speed
Still-air range, which the calculator gives you, assumes no wind - and wind does more than add or subtract from ground range. Into a headwind, the optimal strategy is to speed up a little: flying faster reduces the time the headwind has to push you back, improving ground distance per unit of fuel. With a tailwind, the reverse - slowing slightly lets the tailwind do more of the work. So the true best-range speed over the ground shifts with the wind, which is exactly why real flight planning layers forecast winds aloft on top of the still-air baseline.
Reading the Still-Air Number
Treat the calculator's range as the honest zero-wind reference it is - the number to compare aircraft or sanity-check a route. Then remember it assumes one particular speed and no wind. Fly slower toward the endurance point and you will stay up longer but travel less; speed up toward Carson speed and into a headwind and you will trade fuel for time - and the drag curve underneath is what makes every one of those trades real.
Ready to Put This Into Practice?
Now that you understand how it works, plug in your own numbers and get an instant, accurate result.
Use the Fuel Burn Range Calculator Now →