How to Read a PIREP (and How to File One)

A PIREP is a pilot report: a short, structured account of actual in-flight conditions, filed from an aircraft that is in them. Every other product in your briefing is either a ground observation or a forecast. The PIREP is the only weather product that tells you what the air is doing right now, at altitude, as experienced by a real airframe. A forecast can say icing is possible between 6,000 and 10,000 ft; a PIREP from a Bonanza twenty minutes ahead of you says the tops are at 8,900 and the ice is light rime.

There are two kinds. A routine report is tagged UA. An urgent report, tagged UUA, carries the conditions nobody wants to meet uninformed. The format for both lives in AIM 7-1-18, and once you know the field order you can read any PIREP in a few seconds. Reading them is half the skill. The other half is filing your own, which takes under a minute of radio time and is the closest thing GA has to paying it forward.

The format, field by field

Every PIREP is a chain of slash-delimited fields in a fixed order. Per AIM 7-1-18, the first six are in every report; the rest appear only when there is something to say.

Code	Field	What goes in it
XXX	Station	Nearest weather reporting location to the phenomenon
UA / UUA	Type	Routine or urgent report
/OV	Location	Position relative to a NAVAID or fix: radial and distance, or fix-to-fix
/TM	Time	Four digits, UTC
/FL	Altitude	Three digits, hundreds of feet MSL; UNKN if not known
/TP	Aircraft type	The designator, like C172 or PA28; UNKN if not known
/SK	Sky condition	Cloud coverage with bases and tops
/WX	Weather	Flight visibility, precipitation, restrictions to visibility
/TA	Temperature	Degrees Celsius; M prefix for below zero
/WV	Wind	Direction (magnetic) and speed in knots
/TB	Turbulence	Intensity, and altitudes if layered
/IC	Icing	Intensity and type (rime, clear, mixed)
/RM	Remarks	Anything else worth passing on

One detail trips almost everyone at first: heights in a PIREP are MSL. A METAR reports cloud bases above the ground; a PIREP reports what the altimeter read when the pilot entered the layer. Keep that straight when you compare the two on a briefing.

A worked example, decoded first

Here is what a real report says, in plain English. A Beech 99 flying between Oklahoma City and Tulsa at 1800Z, cruising at 12,000 ft, reports two cloud layers: a broken layer based at 1,800 ft with tops at 5,500, then an overcast based at 7,200 with tops at 8,900, and clear sky above that. Outside air temperature is -7 °C. The wind at altitude is from 080° at 21 knots. The crew felt light turbulence between 5,500 and 7,200 ft, and picked up light to moderate rime ice between 7,200 and 8,900.

That entire paragraph compresses into one line:

UA /OV OKC-TUL/TM 1800/FL120/TP BE99/SK BKN018-TOP055/OVC072-TOP089/CLR ABV
/TA M7/WV 08021KT/TB LGT 055-072/IC LGT-MOD RIME 072-089

Read it slash by slash against the table above and every character resolves. For a pilot planning that route an hour later, this single report answers the questions the forecast can only estimate: where the tops are, whether you can get on top, what the ice is doing inside the layer, and which altitudes are smooth.

What makes a PIREP urgent

A UUA prefix means the report contains weather in a specific set of categories that FAA specialists must handle with priority. Per FAA Order JO 7110.10, the manual flight service specialists work from, a PIREP is classified urgent when it reports any of the following:

• Tornadoes, funnel clouds, or waterspouts
• Severe or extreme turbulence, including clear air turbulence
• Severe icing
• Hail
• Low-level wind shear, meaning shear within 2,000 ft of the surface with airspeed fluctuations of 10 knots or more
• Volcanic ash

When you see UUA on a briefing, stop scrolling and read it. Someone met one of those conditions recently enough that the report is still circulating, and an urgent PIREP can be the observation that triggers a SIGMET. If the distinction between advisory products is fuzzy, our guide to AIRMETs and SIGMETs covers which product warns of what, and for whom.

The intensity words are defined terms

“Moderate turbulence” is not a vibe. The AIM defines each level by what is happening to the airplane, and the definitions are what make one pilot’s report usable by another.

For turbulence (AIM 7-1-21): light momentarily causes slight, erratic changes in altitude or attitude. Moderate brings definite strain against seat belts and dislodges unsecured objects, but the aircraft stays in positive control throughout. Severe causes large, abrupt changes in altitude or attitude with large airspeed variations, and the aircraft may be momentarily out of control. Extreme means the aircraft is practically impossible to control and structural damage is possible. Duration words are defined too: occasional is less than a third of the time, intermittent up to two thirds, continuous more than that. Where the bumps come from in the first place, and how the scale plays out across aircraft types, is in our guide to turbulence types, intensities, and reporting.

For icing (AIM 7-1-19): trace means ice has become noticeable and is building slightly faster than it sublimates, at a reference rate under a quarter inch per hour on the outer wing. Light builds at a quarter inch to an inch per hour, enough to need occasional cycling of deicing equipment. Moderate builds at 1 to 3 inches per hour and demands frequent cycling. Severe means ice is accumulating faster than the protection systems can shed it, and in places they do not cover; by regulation, an immediate exit is required.

Now the caveat that matters for us: these reports are relative to the aircraft that filed them. The AIM itself notes that severe icing is aircraft dependent. That is exactly why /TP is a mandatory field. Moderate turbulence reported by a 737 at 12,000 ft may be a genuinely rough ride in a 172; moderate ice on a King Air with boots is a different problem than moderate ice on an airplane with no protection at all. Always read the type before you weigh the report.

How to file one

You already know five of the six mandatory fields before you key the mic: where you are, what time it is, your altitude, and your aircraft type. The only preparation is deciding what you want to report and roughly organizing it in the PIREP order: position, time, altitude, type, then conditions.

Give the report to whoever you are already talking to. AIM 7-1-18 says to report to the ground facility with which communications are established: center, approach, or tower all accept PIREPs. If you are not talking to anyone, call Flight Service. 122.2 is still the most common frequency, but the FAA begins decommissioning most of its remaining Flight Service radio outlets in September 2026, so check the frequency box on the sectional rather than assuming coverage. On the ground, Flight Service also accepts PIREPs through its web portal. The call is short:

1. “Fort Worth Center, Skyhawk Three Four Five Whiskey Bravo, pilot report.”
2. Position and time: “One five miles southwest of Bowie VOR at two zero one five Zulu.”
3. Altitude and type: “Six thousand five hundred, Cessna one seventy-two.”
4. Conditions: “Tops of the scattered layer at five thousand, smooth, visibility better than ten.”

Do not stress about phraseology. The AIM is explicit that pilots should not be overly concerned with strict format; the point is getting the information relayed so other pilots benefit. The specialist on the other end will format it.

Two things make filing worth the minute it costs. The first pilot it helps is the one behind you, tonight, staring at the same forecast you launched into. The second beneficiary is the forecast itself: PIREPs feed verification of AIRMETs and TAFs and are ingested by the icing and turbulence graphics on aviationweather.gov, so your report sharpens the very products you briefed from. That loop runs through the same self-briefing flow we walk through in our preflight weather briefing guide, and PIREPs are the step most of us skip.

Scarce exactly where we need them

Here is the uncomfortable part. The NTSB looked hard at the PIREP system in a 2017 special investigation report (SIR-17/02) and found chronic underreporting, plus delays and data losses in how reports moved through the system. Airline crews file regularly at the flight levels. Down at 3,000 to 10,000 ft, where GA lives and where the icing layers and the ragged ceilings actually are, reports are thin. The altitudes with the most weather exposure per airframe get the fewest reports.

The fix is not complicated. Make one PIREP per flight a habit, the same way a personal minimums check is a habit. It does not need to be dramatic weather; a report of smooth air and clear skies above a deck is real information to a pilot deciding whether to climb through it, and FAA facilities actively solicit reports whenever ceilings are at or below 5,000 ft, visibility at the surface or aloft is at or below 5 miles, or there are thunderstorms, light or greater icing, moderate or greater turbulence, wind shear, or volcanic ash around (AIM 7-1-18). If conditions were interesting enough that you would mention them at the FBO desk, they were interesting enough to file. Say it on frequency instead, where the next pilot can actually use it.

Common questions

Are PIREP altitudes MSL or AGL?

MSL. A PIREP reports what the altimeter read when the pilot entered a layer, while a METAR reports cloud bases above the ground. That difference trips up almost everyone at first, and it matters most when you are comparing a reported cloud base against the ceiling in a surface observation for the same field.

Who do I give a PIREP to?

Whoever you are already talking to. AIM 7-1-18 says to report to the ground facility with which communications are established, so center, approach and tower all accept them. If you are not talking to anyone, call Flight Service, but check the frequency box on the sectional rather than assuming 122.2 works, because the FAA is decommissioning most remaining radio outlets.

Does moderate turbulence mean the same thing in every aircraft?

No, and that is why aircraft type is a mandatory field. The AIM defines the intensities by what happens to the airplane, and it notes explicitly that severe icing is aircraft dependent. Moderate turbulence reported by a 737 at 12,000 ft can be a genuinely rough ride in a 172. Read the type before you weigh the report.