Commercial pilot · ACS CA.I.C
Weather Information (Commercial)
A commercial pilot uses the same weather products as a private pilot, but with more at stake: passengers or cargo, a schedule and a customer. This lesson covers the sources, the products, the meteorology and the decisions.
Why this one matters
Weather accidents in commercial flying usually begin on the ground: a paying passenger, a schedule, and a forecast that is almost good enough. The commercial pilot who decides with written personal minimums, and diverts early without apology, keeps the customer, the airplane and the certificate.
Can’t miss
- •Before beginning any flight, become familiar with all available information concerning it. For a flight under IFR or not in the vicinity of an airport, that includes weather reports and forecasts, fuel requirements, alternatives if the flight can't be completed, and known ATC delays; for every flight, runway lengths and takeoff and landing distances.(14 CFR 91.103(a)-(b))
- •Sources: Flight Service (1-800-WX-BRIEF or online), aviationweather.gov and approved providers. Use reports (METAR, SPECI, PIREP) and forecasts (TAF, GFA, AIRMET, SIGMET) together.(AIM, Chapter 7, Section 1 (meteorology))
- •A forecast is a best guess with a time window. Plan around the worst reasonable case for your arrival time, not the best.(Aviation Weather Handbook (FAA-H-8083-28A))
- •Set personal minimums before you see the weather, and keep them when a customer is waiting.(Risk Management Handbook (FAA-H-8083-2A))
- •Datalink NEXRAD is a mosaic: total latency is commonly 5-15 minutes or more, and the weather can be 15-20 minutes older than the age shown. Use it to stay well clear of storms, never to pick a path between cells.(AIM 7-1-9 and 7-1-11 (FIS-B and in-cockpit weather); NTSB Safety Alert SA-017)
- •Divert early, while you still have fuel, daylight and options. A diversion is a normal outcome, not a failure.(Risk Management Handbook (FAA-H-8083-2A))
- •Avoid known or forecast icing unless the airplane is approved for it, and severe turbulence in any airplane.(Aviation Weather Handbook (FAA-H-8083-28A))
What you should know
Sources and products K1 · K2
- Briefings: a standard briefing is the complete one, for a flight not yet briefed; an abbreviated briefing supplements or updates one you already have; an outlook briefing is for a flight more than 6 hours away and doesn't replace a standard briefing closer to departure.(AIM 7-1-4; AC 91-92)
- Reports: METAR and SPECI (airport observations), PIREPs (what pilots actually found: tops, icing, turbulence). Forecasts: TAF, the Graphical Forecasts for Aviation, winds and temperatures aloft.(Aviation Weather Handbook (FAA-H-8083-28A))
- AIRMETs (moderate hazards): Sierra, ceilings under 1,000 feet or visibility under 3 SM over a wide area, and extensive mountain obscuration; Tango, moderate turbulence, sustained surface winds of 30 knots or more, and non-convective low-level wind shear; Zulu, moderate icing and freezing levels.(Aviation Weather Handbook (FAA-H-8083-28A); AIM 7-1-6)
- SIGMETs (severe hazards, any aircraft): severe or extreme turbulence or clear air turbulence and severe icing not tied to thunderstorms, widespread dust or sandstorms below 3 SM, and volcanic ash. Convective SIGMETs: lines of thunderstorms, embedded thunderstorms, thunderstorms covering a large area at high intensity, and severe surface weather (tornadoes, large hail, surface winds of 50 knots or more).(Aviation Weather Handbook (FAA-H-8083-28A); AIM 7-1-6)
- Surface Analysis Chart: fronts, pressure systems and station plots, the big picture. Ceiling and Visibility Analysis (CVA): current ceilings and visibilities between reporting stations.(Aviation Weather Handbook (FAA-H-8083-28A))
- Convective Outlook (AC) from the Storm Prediction Center: where thunderstorms, and severe ones, are expected over the next days; use it for planning the day, not the route minute by minute.(Aviation Weather Handbook (FAA-H-8083-28A))
Meteorology on the route K3
- Know the hazards for each phase: fog and low ceilings at departure and arrival, fronts and convection en route, mountain wave and turbulence over terrain.(Aviation Weather Handbook (FAA-H-8083-28A))
- Stability decides the weather: stable air gives smooth air and poor visibility; unstable air gives turbulence, good visibility and convection.(Aviation Weather Handbook (FAA-H-8083-28A))
- Temperature and dew point close together mean fog or low clouds are likely, especially as the air cools at night.(Aviation Weather Handbook (FAA-H-8083-28A))
- Heat and moisture: the sun heats the ground and the ground heats the air; air cools about 2°C per 1,000 feet when dry and less when saturated. Cooling to the dew point brings clouds, fog and precipitation.(Aviation Weather Handbook (FAA-H-8083-28A))
- Air masses and fronts: a cold front brings a narrow band of showers or thunderstorms and gusty wind shifts; a warm front, wide areas of low ceilings, rain and poor visibility; stationary and occluded fronts mix the two.(Aviation Weather Handbook (FAA-H-8083-28A))
- Clouds tell you the air: cumulus means unstable air and bumps; stratus, stable air and low ceilings; towering cumulus and cumulonimbus, convection to avoid.(Aviation Weather Handbook (FAA-H-8083-28A))
- Thunderstorms need moisture, unstable air and a lifting force. Stay at least 20 nm from severe ones. Microbursts are short, violent downdrafts with wind shear: a headwind gain followed by a strong downdraft and tailwind, near the ground.(Aviation Weather Handbook (FAA-H-8083-28A))
- Wind shear can come with fronts, thunderstorms, temperature inversions and mountain wave; expect it near the surface when strong winds sit over calm air.(Aviation Weather Handbook (FAA-H-8083-28A))
- Icing needs visible moisture at or below freezing: check the freezing level, and know that the worst icing is often just below it in freezing rain, or in clouds near the tops of cumulus.(Aviation Weather Handbook (FAA-H-8083-28A))
- Frost on the wings, even thin, disrupts the airflow and can stop the airplane from flying: remove it all before takeoff.(Aviation Weather Handbook (FAA-H-8083-28A))
- Obstructions to visibility: haze, smoke, dust and volcanic ash reduce visibility, especially looking into the sun, and ash can stop an engine.(Aviation Weather Handbook (FAA-H-8083-28A))
Datalink and onboard weather K4 · R2
- FIS-B over ADS-B gives METARs, TAFs, NEXRAD and more for free, but the radar picture is a mosaic and can be well behind real time.(AIM 7-1-9 and 7-1-11 (FIS-B and in-cockpit weather))
- Onboard weather equipment (lightning detectors, onboard radar) has its own limits: know what yours shows and what it misses.(Your airplane's POH/AFM)
- Limits of the products: a METAR or SPECI is one point at one moment; AWOS and ASOS can miss clouds and weather beyond their sensors; PIREPs are sparse and subjective; a TAF covers about 5 statute miles around one airport and is amended as it changes.(Aviation Weather Handbook (FAA-H-8083-28A))
- In flight, update with Flight Service, ATC's hazardous weather broadcasts, Center Weather Advisories and PIREPs, and give PIREPs yourself. ATIS is for the airport you're arriving at, not the route.(AIM, Chapter 7, Section 1 (meteorology); Aviation Weather Handbook (FAA-H-8083-28A))
Go, no-go and divert R1
- Write personal minimums (ceiling, visibility, wind, crosswind, night) and decide against them, not against the customer’s schedule.(Risk Management Handbook (FAA-H-8083-2A))
- Set a divert trigger before you leave: a ceiling, a visibility, a fuel number or a time. When it happens, divert.(Risk Management Handbook (FAA-H-8083-2A))
- Known or forecast icing and turbulence aloft are reasons to change the plan, the altitude or the day.(Aviation Weather Handbook (FAA-H-8083-28A))
Scenarios
Decide what you would do first, then see the worked answer.
An AIRMET Zulu covers your route at your planned altitude. The airplane isn’t approved for known icing.
What changes? See the worked answer
Plan an altitude or route that stays out of cloud in the freezing range, with an escape, or postpone.
Aviation Weather Handbook (FAA-H-8083-28A)
En route, the destination reports a ceiling falling below your trigger. You have fuel for an hour.
What do you do? See the worked answer
Divert now to the alternate while fuel and options are still good, and tell the passengers why.
Risk Management Handbook (FAA-H-8083-2A)
Your screen shows a clear path between two red cells ahead.
Take it? See the worked answer
No. The image can be many minutes old. Deviate wide, ask ATC what they see, or land.
AIM 7-1-9 and 7-1-11 (FIS-B and in-cockpit weather)
Common mistakes
Letting the schedule set the minimums.
Pressure lowers standards one flight at a time.
Instead: Write minimums down and decide before you meet the customer.
Treating datalink radar as real time.
It can be many minutes old.
Instead: Use it for wide avoidance only.
Diverting late.
Fuel and daylight run out.
Instead: Set a divert trigger before departure.
Now train it
Say it out loud, hear it asked, and take the quick check in this lesson’s practice pack. It tracks your shaky spots.
Got it?
When it feels solid, practice weather information (commercial) out loud with our examiner.
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Sources
- Aviation Weather Handbook (FAA-H-8083-28A)
- Aeronautical Information Manual (AIM): Chapter 7
- Risk Management Handbook (FAA-H-8083-2A): Personal minimums
- 14 CFR: 91.103
- Commercial Pilot ACS (FAA-S-ACS-7B): Area I, Task C
Study aid, not FAA guidance. Regulations change; check the current text at eCFR and the ACS. Checked against current sources 2026-11-13.