What is a Winds Aloft Forecast (FB) and why does it matter for drone pilots?

A Winds Aloft Forecast, abbreviated FB (from the French 'Vent en altitude'), is an FAA weather product that provides predicted wind direction, wind speed, and temperature at various altitudes above ground level. For remote pilots, it is especially useful because headwinds and tailwinds directly affect drone groundspeed, flight time, and battery consumption. The Aviation Weather Handbook notes that winds aloft data are derived from upper-air observations and numerical weather prediction models, making them reliable planning tools. By reviewing the FB before a flight, a remote pilot can anticipate adverse wind conditions and adjust mission timing or route accordingly.

How do you read a Winds Aloft Forecast for a drone flight below 400 feet AGL?

FB forecasts are issued for standard altitude levels beginning at 3,000 feet MSL, so drone pilots must interpolate expected surface-to-400-foot winds by comparing the 3,000-foot forecast value with nearby surface observations from METARs or Automated Weather Observing System reports. Wind direction in an FB is expressed in true degrees (not magnetic), and speeds are in knots, so pilots should be aware of that distinction when planning. If the FB shows a four-digit group beginning with '9900,' that indicates light and variable winds with no significant forecast speed. Cross-referencing the FB with local surface weather products gives remote pilots the most complete picture of low-altitude wind conditions relevant to sUAS operations.

What's the difference between a Winds Aloft Forecast and a Terminal Aerodrome Forecast for drone flight planning?

A Terminal Aerodrome Forecast (TAF) predicts surface-level weather conditions — including wind, visibility, and sky condition — within a 5-statute-mile radius of a specific airport, whereas a Winds Aloft Forecast provides predicted winds and temperatures at multiple altitude levels over a broader geographic area. For drone operations, a TAF is most useful for understanding conditions right at the surface near an airport environment, while the FB helps a remote pilot assess how winds may increase or shift with altitude, even within the low altitudes sUAS typically operate. The Pilot's Handbook of Aeronautical Knowledge emphasizes that wind speed generally increases with altitude, so reviewing both products together gives the most accurate situational awareness. Remote pilots preparing for the FAA Unmanned Aircraft General — Small Unmanned Aircraft Systems Knowledge Test should understand how to interpret and apply both weather products.

Winds Aloft Forecasts (FB Winds) and Drone Flight Planning

Before every drone flight, a professional remote pilot does more than glance at a smartphone weather app. One of the most informative — and commonly underused — preflight weather tools available is the Winds and Temperatures Aloft Forecast, formally called the FB winds forecast (from its old teletype product code, "FB"). This forecast predicts wind direction, wind speed, and air temperature at a series of altitude levels above the surface, covering the next several hours across a wide geographic area. For Part 107 remote pilots operating sUAS (small unmanned aircraft systems) at altitudes up to 400 feet AGL — and in some cases higher with waiver — understanding how to read and apply FB winds data is both an FAA knowledge test topic and a genuine flight safety skill.

This article walks you through exactly what the FB winds forecast contains, how to decode it, why it matters to drone operations specifically, and how to avoid the traps the FAA written test loves to set for unprepared candidates.

What the Winds Aloft Forecast Contains

The FB winds forecast is issued by the Aviation Weather Center (AWC) and is available through official sources including aviationweather.gov. Forecasts are issued four times daily — based on 00Z, 06Z, 12Z, and 18Z observation times — and cover forecast periods of 6, 12, and 24 hours. Each forecast applies to a specific valid time window, so you must always check that the forecast you are reading is valid for your planned flight time.

The data is organized by forecast station (a three-letter identifier representing a geographic location) and by altitude level. Standard altitude levels in the contiguous United States include 3,000 feet MSL, 6,000 feet MSL, 9,000 feet MSL, 12,000 feet MSL, and continuing upward through the flight levels. For most drone operations, the 3,000-foot level is the most directly relevant, since it is the lowest reporting level and gives the best approximation of what is happening in the lower atmosphere — though even 3,000 feet MSL may be far above your drone's operating altitude of 400 feet AGL.

How to Decode the FB Winds Format

The raw FB winds product uses a compact four- or six-digit code for each altitude entry. Understanding this code is essential for passing the FAA Part 107 knowledge test. Here is how to decode a typical entry:

Wind direction (first two digits): Represents the true direction from which the wind is blowing, in tens of degrees. For example, "23" means 230° true. Note carefully: this is true north orientation, not magnetic. This differs from surface wind reports in METARs and ATIS, which are given in magnetic direction.
Wind speed (next two digits): Expressed in knots. So "2318" means wind from 230° true at 18 knots.
Temperature (last two digits with sign): In degrees Celsius, always negative above 24,000 feet MSL (the sign is dropped above that level by convention). Below 24,000 feet, a minus sign is included when the temperature is below zero. For example, "2318+05" decodes as 230° true, 18 knots, +5°C.

There are two important special codes to recognize:

Light and variable winds: When the entry reads "9900," it means winds are light and variable (less than 5 knots), and no temperature data is included at that level.
Winds above 100 knots: When wind speed reaches 100 knots or more, 50 is added to the direction code and 100 is subtracted from the speed. For example, an entry of "7545" decodes as: 75 minus 50 = 25, so direction is 250° true; 45 plus 100 = 145 knots. This encoding convention is a frequent FAA test question.
No data available: Entries may show "////" or similar placeholders when data is missing for that level at that station.

Why FB Winds Matter for Drone Operations

You might wonder: if drones fly at 400 feet AGL and the lowest FB winds level is 3,000 feet MSL, why bother? The answer is that the winds aloft forecast still provides critically useful information for sUAS pilots, for several reasons.

Understanding the Wind Profile

Surface winds are reported in METARs, but those readings represent conditions at approximately 10 meters (33 feet) above ground level at the observing station — which may be miles from your flight location. The FB winds forecast helps you understand the gradient of the wind: how wind speed and direction are changing as you climb. If the forecast shows calm surface winds but 25-knot winds at 3,000 feet, you can reasonably infer that winds may be increasing significantly as your drone climbs toward 400 feet AGL — particularly over flat, open terrain with few obstacles to slow the flow.

Battery Life and Flight Time

Wind is the single biggest variable affecting drone battery consumption. A multirotor drone fighting a 20-knot headwind on a return trip may consume two to three times as much battery power as it would in calm air. By consulting FB winds before flight, you can anticipate the wind environment, adjust your flight plan to keep the drone closer to home in the upwind direction, and set more conservative battery return-to-home thresholds. Underestimating wind strength is one of the leading causes of flyaway incidents and flyaways that end in loss of the aircraft.

Turbulence and Mechanical Mixing

Strong winds aloft combined with surface heating create conditions favorable for mechanical turbulence — especially downwind of buildings, trees, ridge lines, and other obstructions. When the FB winds show strong flow over terrain near your planned operating area, be alert for rotor turbulence and gusty, variable conditions at low altitude that could destabilize a small drone.

Temperature Effects on Performance

The temperature data in the FB winds forecast feeds into your understanding of density altitude. High temperatures at altitude reduce air density, which degrades rotor efficiency and reduces the maximum payload and speed capability of the aircraft. In hot summer conditions, even at modest elevations, a drone operating at or near its performance limits may struggle to maintain controlled flight.

Key Numbers and Rules

FB winds are in true degrees, not magnetic. Surface METAR winds are magnetic. Know the difference — the test will contrast them.
3,000 feet MSL is the lowest altitude level reported in standard FB winds products for the contiguous US.
Temperature data is omitted only near station elevation: temperature is not forecast for a level if that level is within 2,500 feet of the issuing station's field elevation. At many stations, this means the 3,000-foot level may still include a temperature value if the station is low enough; it is not a fixed rule that temperature never appears below 6,000 feet.
"9900" means light and variable winds, less than 5 knots.
Add 50 to direction, subtract 100 from speed when winds exceed 99 knots — reconstruct by reversing those steps.
FB winds use UTC (Zulu) time. Always convert to local time when cross-checking your planned flight window.
Valid time vs. issuance time: The forecast is issued four times daily, but is not instantly valid — check the header for the valid period, not just the issuance time.

Using FB Winds in Preflight Planning

A practical workflow for a Part 107 remote pilot might look like this: first, obtain the FB winds forecast from aviationweather.gov for the station closest to your flight location. Identify the 3,000-foot MSL level entry and decode the wind direction (remembering it is true), speed in knots, and any temperature data available at higher levels. Then compare this to surface wind data in the METAR or Terminal Aerodrome Forecast (TAF) for the area. If there is a large difference between surface and 3,000-foot winds, anticipate increasing wind speeds as the drone climbs. Plan your mission route so the outbound leg travels into the wind and the return leg is with the wind — ensuring maximum battery reserves for the return trip when the drone is most likely to need it.

Also note that aviationweather.gov now provides a graphical winds aloft display, which shows wind barbs plotted on a map at selected altitude levels. This visual format is often easier to interpret quickly during planning than the raw text product, though understanding the text format remains required for the knowledge test.

Common Test Traps

Confusing true and magnetic direction: FB winds direction is in true degrees. Surface winds in METARs are in magnetic degrees. Many test questions are designed to catch pilots who treat them interchangeably.
Misreading the high-wind encoding: When the first two digits of a winds entry are greater than 36 (e.g., "73"), that is the signal that 50 has been added to the direction and 100 subtracted from the speed. Forgetting to apply this conversion leads to wildly wrong answers.
Assuming 9900 means calm: "9900" means light and variable — not perfectly calm. There may still be a few knots of wind shifting in direction, which matters for small, lightweight drones.
Ignoring the valid time: Using a forecast that has expired — or that applies to a different time window than your flight — provides false assurance. Always verify the forecast valid period in the header.
Assuming temperature is never shown at low levels: Temperature data is omitted only when a level is within 2,500 feet of the station's field elevation — it is not universally excluded from the 3,000-foot level. Always check the specific station and level rather than assuming a fixed cutoff.