If the engine stops, height becomes your fuel. How far you can glide depends on the aircraft’s glide ratio, your height above the ground, and the wind. Knowing the numbers before you need them tells you which fields are within reach and which are not. Work out your still-air and wind-corrected range with the Glide Distance Calculator.
Glide ratio in one line
A glide ratio of 9:1 means the aircraft travels 9 units forward for every 1 unit of height it loses, in still air, at its best glide speed. One nautical mile is 6,076 ft, so:
Still-air glide distance (NM) = height above ground (ft) × glide ratio ÷ 6,076
Many light singles have a best-glide ratio around 8:1 to 10:1. The exact figure is in your aircraft flight manual, sometimes as a glide-distance chart rather than a ratio.
Still-air glide distance
| Height above ground | Ratio 9:1 | Ratio 12:1 |
|---|---|---|
| 2,000 ft | 3.0 NM | 3.9 NM |
| 4,000 ft | 5.9 NM | 7.9 NM |
| 6,000 ft | 8.9 NM | 11.8 NM |
| 8,000 ft | 11.8 NM | 15.8 NM |
| 10,000 ft | 14.8 NM | 19.7 NM |
A useful shortcut for a 9:1 aircraft is about 1.5 NM per 1,000 ft above the ground.
The wind changes everything
The glide ratio is relative to the air. Over the ground, a headwind shortens the glide and a tailwind stretches it, in proportion to groundspeed:
Glide distance over the ground = still-air distance × groundspeed ÷ true airspeed
Worked example
A light single with a 9:1 glide ratio and a best-glide speed of 70 kt loses its engine at 6,000 ft above the ground. The wind is 20 kt.
- Still air: 6,000 × 9 ÷ 6,076 = 8.9 NM.
- Gliding into a 20 kt headwind, groundspeed is 50 kt: 8.9 × 50 ÷ 70 = 6.3 NM.
- Gliding with a 20 kt tailwind, groundspeed is 90 kt: 8.9 × 90 ÷ 70 = 11.4 NM.
The reachable area is not a circle around you. It is stretched downwind, so a field 9 NM upwind may be out of reach while one 10 NM downwind is not.
Things that cut the glide short
- Flying faster or slower than best glide. Either way the ratio gets worse. Trim for best glide speed first.
- Weight. In many aircraft the best-glide speed is lower at lighter weights. The flight manual gives the figure for maximum weight.
- Drag. Extended flaps, gear, a windmilling propeller or a slip all steepen the glide. Some manuals give a better figure with the propeller stopped or at coarse pitch.
- Turns. Each turn costs height. A 360° turn can use several hundred feet.
- Using height above sea level. The calculation needs height above the ground at the landing area, not altitude on the altimeter.
Planning with glide range
Before flying over water, mountains or built-up areas, check how high you need to be to keep a landing area within reach. A common approach is to plan a margin of at least 1,000 ft for the circuit and approach at the landing site, which means using only part of the computed range. Picking a higher cruising level is often the cheapest safety margin a pilot can buy.
FAQ
Does weight change the glide ratio?
Not much. Weight mainly changes the best-glide speed. Flown at the right speed for its weight, a heavy or light aircraft glides about the same distance in still air. Wind changes that, because the slower light aircraft is affected more by a headwind.
What is a typical airliner glide ratio?
Large jets are commonly around 15:1 to 20:1 clean, depending on type and configuration.
Should I use the glide ratio or the manual’s chart?
The chart, when your manual has one. It reflects tested conditions for your type. The ratio is a planning approximation.
Sources and further reading
FAA Airplane Flying Handbook (FAA-H-8083-3), chapter on emergency procedures, and the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25). Always use your aircraft flight manual for best-glide speed and distance.
Last reviewed: November 2026.