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ATIS, AWOS, and ASOS Explained: How to Get Airport Weather and Use It Correctly

Updated: 6 days ago

ATIS, AWOS, and ASOS are the three primary systems that deliver real-time airport weather to pilots. Every approach, every departure, every flight involves checking one of them — but most pilots can't explain the differences, when to use each, the AWOS classification levels, or the proper phraseology when checking in with ATC. Understanding these systems isn't just academic — it affects how you make decisions about runway use, altimeter setting, and whether you can legally fly the planned approach.


This post covers all three systems in practical depth: what each provides, how to access it, the AWOS classification levels, D-ATIS, proper phraseology, and how to use airport weather information effectively.



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ATIS — Automatic Terminal Information Service

ATIS is a continuous broadcast of recorded airport information at busier airports. It serves to reduce ATC frequency congestion by automating the routine information that every arriving and departing pilot needs.


Where you'll find ATIS:

ATIS is typically available at:

  • Class B airports (always)

  • Class C airports (almost always)

  • Class D airports with sufficient traffic volume

  • Some Class E (uncontrolled) airports with significant operations


You won't find ATIS at small uncontrolled fields — those typically use AWOS or ASOS instead.


What ATIS includes:

The ATIS broadcast typically follows a standard format:

  1. Airport identifier and "information" letter — "Salt Lake City International Airport, information Bravo"

  2. Time of issuance — "1854 Zulu" or "1054 Mountain"

  3. Weather — wind, visibility, ceiling, temperature, dewpoint, altimeter

  4. Approach in use — "ILS approach to runway 16L in use"

  5. Runways in use — "Landing and departing runway 16L and 16R"

  6. Significant NOTAMs — runway closures, taxiway closures, special procedures

  7. Special instructions — noise abatement, hot spots, frequency changes

  8. Closing statement — "Advise on initial contact you have information Bravo"


The information letter sequence:

  • Each new ATIS update gets the next letter in the phonetic alphabet

  • Bravo → Charlie → Delta → Echo, etc.

  • After Zulu, the sequence restarts with Alpha

  • The letter changes when the broadcast is updated, not on a regular schedule


When ATIS is updated:

  • At least every 60 minutes

  • More frequently when weather changes (typically with each new METAR)

  • When operational changes occur (runway changes, approach changes)

  • A "special" update may be made for significant changes between regular updates


Pilot use:

  • Check ATIS before contacting ATC

  • Note the information letter

  • Inform the controller you have it: "with information Bravo"

  • This tells ATC you have current information and saves them from re-broadcasting it


D-ATIS — Digital ATIS

A modern variant of ATIS that delivers the same information through digital text and data link rather than (or in addition to) voice.


How D-ATIS works:

  • Same content as voice ATIS

  • Delivered through ACARS (Aircraft Communications Addressing and Reporting System) on transport aircraft

  • Or through datalink on ADS-B-equipped aircraft

  • Can be requested by aircraft equipped with the right systems


Advantages of D-ATIS:

  • No need to listen to a recorded broadcast

  • Pilot can read at their own pace

  • Information is text-based (eliminates audio transcription errors)

  • Available continuously regardless of frequency interference


Where D-ATIS is available:

  • Most major Class B airports in the U.S.

  • Selected Class C airports

  • Increasingly common as ADS-B systems mature

  • Found on the airport diagram or through approach plates


For GA pilots:

  • Most light GA aircraft don't have ACARS

  • Some EFB apps can pull D-ATIS via ADS-B FIS-B

  • For most GA pilots, the standard voice ATIS remains the primary access method


AWOS — Automated Weather Observing System

AWOS provides automated, real-time weather observations primarily at smaller airports without full-time weather observers or significant traffic.


Where you'll find AWOS:

  • Smaller GA airports

  • Class E airports with regular IFR traffic

  • Many Class D airports without ATIS

  • Some uncontrolled fields


AWOS Classifications:

The capabilities of an AWOS depend on its classification level. The FAA uses standardized levels:


AWOS-A — The most basic

  • Altimeter setting only

  • No other weather information

  • Often at smaller fields with limited operations

AWOS-A/V — Basic with visibility

  • Altimeter and visibility

  • Slightly more capable than AWOS-A

AWOS-1 — Basic weather

  • Altimeter

  • Wind speed, direction, gusts

  • Temperature

  • Dewpoint

  • Density altitude

AWOS-2 — AWOS-1 plus visibility

  • Everything from AWOS-1

  • Plus visibility

AWOS-3 — AWOS-2 plus cloud information

  • Everything from AWOS-2

  • Plus cloud height (ceiling) up to 12,500 feet

  • Plus sky condition

AWOS-3P — AWOS-3 plus precipitation

  • Everything from AWOS-3

  • Plus precipitation type identification (rain, snow)

AWOS-3PT — AWOS-3P plus thunderstorm

  • Everything from AWOS-3P

  • Plus thunderstorm and lightning detection

AWOS-3T — AWOS-3 plus thunderstorm

  • AWOS-3 with thunderstorm detection

  • May not include precipitation type

AWOS-4 — Most comprehensive AWOS

  • Everything from AWOS-3PT

  • Plus runway visual range (RVR)

  • Plus other specialized capabilities


Why this matters: When you're planning a flight to an unfamiliar airport, knowing what level of AWOS is installed tells you what information you'll get. AWOS-A only gives you altimeter — you won't get ceiling or visibility, so additional weather sources will be needed for IFR operations.


How to access AWOS:

  • Radio frequency: Tune the AWOS frequency listed in the chart supplement or on the airport diagram

  • Phone number: Many AWOS systems have a phone number for pre-flight checking

  • EFB integration: ForeFlight, Garmin Pilot, and other apps display AWOS information


Update frequency:

  • Typically every minute

  • Reports current conditions, not forecasts

  • Significant changes trigger immediate updates


ASOS — Automated Surface Observing System

ASOS is a more comprehensive automated observation system, jointly operated by the FAA, NWS (National Weather Service), and DOD. It provides the official weather observations that feed into METARs and other aviation weather products.


Where you'll find ASOS:

  • Class C and Class B airports (most)

  • Major regional airports

  • Locations with consistent commercial operations

  • Some Class D airports with significant operations


ASOS capabilities (more comprehensive than AWOS):

  • Wind speed, direction, and gusts

  • Temperature and dewpoint

  • Altimeter setting

  • Visibility (multiple sensors at busier airports)

  • Cloud height and sky condition

  • Precipitation type (rain, snow, freezing rain, hail)

  • Precipitation accumulation (hourly and daily)

  • Pressure tendency

  • Thunderstorm and lightning detection

  • Sometimes RVR at major airports


The reporting hierarchy:

  • Routine: Hourly METARs based on the previous hour's observations

  • Special (SPECI): Issued when conditions change significantly

  • Real-time: Continuous updates available via radio or phone


ASOS feeds the METAR system: The hourly METAR you read in your weather briefing is typically generated from the ASOS observation at that airport. The official record keeping starts with ASOS data.


Access methods:

  • Radio frequency: Continuous broadcast on a dedicated frequency

  • Phone: Each ASOS has a dedicated phone number

  • Datalink: Available through FIS-B (free with ADS-B), XM Weather, and similar

  • EFB apps: ForeFlight, Garmin Pilot, and others display ASOS data


Key conceptual difference:

  • ATIS is operational information (weather + airport status) at busier airports

  • AWOS/ASOS are weather-only, automated observations at any airport


Why some airports have both: A larger airport might have ASOS providing the meteorological data and an ATIS broadcast that includes the ASOS-derived weather plus operational information. The ASOS feeds into the ATIS message.


Phraseology: Using ATIS Correctly

The proper way to inform ATC you have ATIS information:

  • Initial contact (departure): "Centennial Tower, Cessna 12345, ready for taxi, with information Bravo."

  • Initial contact (arrival): "Centennial Tower, Cessna 12345, 10 miles south, inbound for landing, with information Bravo."


Common errors:

  • Saying "with the ATIS" without specifying the letter

  • Saying "with information Bravo" but having an older letter

  • Forgetting to update the information letter when the ATIS changes during your flight


When ATIS updates during your flight:

  • Listen for new ATIS information periodically

  • Tower may announce: "Advise have new ATIS Charlie"

  • Update your call: "Centennial Tower, Cessna 12345, with new ATIS Charlie"


Reading Cloud Information

ATIS, AWOS, and ASOS all report cloud information using the same METAR codes:

Code

Meaning

SKC or CLR

Sky clear

FEW

Few (1/8 - 2/8 sky covered)

SCT

Scattered (3/8 - 4/8)

BKN

Broken (5/8 - 7/8) — ceiling

OVC

Overcast (8/8) — ceiling

VV

Vertical visibility (sky obscured)

The number after the abbreviation is altitude in hundreds of feet AGL above the airport.


Examples:

  • "FEW 020 SCT 080" — Few clouds at 2,000 feet AGL, scattered at 8,000 feet AGL

  • "BKN 005 OVC 015" — Broken at 500 feet, overcast at 1,500 feet — IFR ceiling

  • "VV 003" — Vertical visibility 300 feet


Determining ceiling: The lowest BKN, OVC, or VV layer is the ceiling. FEW and SCT layers don't constitute a ceiling.


Practical Pilot Use

Pre-flight (departure):

  • Check ATIS/AWOS/ASOS at departure airport

  • Get current weather, runway in use, altimeter setting

  • Ensure conditions are within your aircraft's and your personal minimums

  • Verify expected runway and pattern direction

  • Note any operational issues (closed taxiways, NOTAMs)


During flight:

  • Listen to ATIS or check ASOS at intermediate airports en route if needed

  • Most useful for fuel stops or weather reassessment

  • Datalink ATIS information available via EFB apps in some cases


Pre-arrival:

  • Check ATIS at destination 30-50 miles out

  • Get information letter and current conditions

  • Choose appropriate approach if IFR

  • Plan landing pattern entry

  • Note runway in use for traffic pattern


Approach phase:

  • ATIS provides runway, approach in use, and weather

  • Inform ATC: "...with information [letter]"

  • Adjust approach plan based on actual weather vs. forecast

  • If conditions are below minimums, request alternate or hold


Common phraseology:

  • "Have information Bravo" — letting ATC know

  • "Information current" — assuring ATC you have it

  • "Last ATIS check at..." — if there's a question about update timing


When the System Is Out of Service

ATIS, AWOS, and ASOS systems can be unavailable due to maintenance, equipment failure, or outages.


ATIS Out of Service:

  • ATC will provide weather information directly on initial contact

  • May increase ATC workload

  • Pilots should request weather and runway/approach information


AWOS/ASOS Out of Service:

  • May be reported in NOTAMs

  • Adjacent airport's weather may need to be used as substitute

  • IFR pilots may need a different alternate

  • Check NOTAMs before flight


Special procedures:

  • ATC can provide special weather observations (called SPECI)

  • Pilots can request observations from FSS

  • Tower controllers at the airport may have visual confirmation of conditions


Common Misconceptions

  • "ATIS gives me a forecast." No — ATIS reports current conditions only. Use TAFs for forecasts.

  • "AWOS is less accurate than ASOS." Not necessarily — both use similar sensors. AWOS may have less comprehensive capability (fewer parameters), but the data it reports is generally accurate.

  • "I only need to check ATIS once before the flight." No — ATIS updates throughout the day. Check current ATIS before any approach.

  • "AWOS information is suitable for IFR alternates." Yes, AWOS-3 and above provide ceiling and visibility data sufficient for IFR alternate qualification. AWOS-A and AWOS-A/V do not.

  • "All AWOS systems report the same things." No — capability varies dramatically with classification level. Check what you're getting.


On the Written Test and Checkride

ATIS, AWOS, and ASOS appear consistently on tests and oral exams. The most commonly tested topics:

  • Differences between ATIS, AWOS, and ASOS

  • ATIS information letter sequence

  • AWOS classification levels (1, 2, 3, 4)

  • Use of "with information Bravo" phraseology

  • Cloud coverage codes (FEW, SCT, BKN, OVC)

  • Determining ceiling from cloud reports

  • When systems are out of service


AWOS Classifications:

  • AWOS-A: Altimeter only

  • AWOS-A/V: Altimeter + visibility

  • AWOS-1: Basic weather (no visibility)

  • AWOS-2: Adds visibility

  • AWOS-3: Adds cloud height

  • AWOS-3P: Adds precipitation type

  • AWOS-3T: Adds thunderstorm detection

  • AWOS-3PT: Comprehensive

  • AWOS-4: Most advanced (RVR, etc.)


ATIS phraseology:

  • "With information [letter]" on initial contact

  • Update letter when ATIS changes during flight

  • Listen for "advise have new ATIS"


Cloud codes:

  • FEW, SCT, BKN, OVC, VV

  • BKN, OVC, VV constitute a ceiling

  • FEW, SCT do not



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Author: Nathan Hodell

CFI, CFII, MEI, ATP, Creator and CEO

Nathan is an aviation enthusiast with thousands of hours of flying and dual instruction over the past 15+ years. Through his aviation career he has been able to earn his ATP, fly as an airline pilot, own/operate flight schools, and create and host wifiCFI.



 
 
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