The FAA has updated its guidance on how pilots and operators can use Real-Time Mesoscale Analysis (RTMA) weather data when automated airport weather sensors fail. The revision responds directly to feedback from operators who have been using the system since it was first introduced a decade ago.
If you’ve ever had a flight delayed because an airport’s temperature sensor stopped working, this is the system designed to fix that problem. Here’s what changed — and why it matters.
What Is RTMA?
Most airports in the U.S. rely on automated weather systems — ASOS (Automated Surface Observing System) or AWOS (Automated Weather Observing System) — to provide real-time surface weather reports. These systems measure temperature, pressure, wind, visibility, and ceiling height, and feed that data into METARs that pilots and dispatchers use for flight planning.
When a sensor fails and there’s no human weather observer to back it up, the airport effectively loses its official weather report for that element. Under FAA regulations, that missing data can force delays, diversions, or cancellations — even when the actual weather is perfectly flyable.
Temperature has historically been the biggest culprit. According to Airlines for America, temperature was the missing element in 85% of weather observation failures affecting aircraft operations.
The RTMA is the backup. Developed by NOAA’s National Weather Service in partnership with the FAA, it’s an hourly analysis system that combines data from surrounding observation stations and weather models to estimate surface weather conditions at airports across the U.S. It covers roughly 540 Part 139 airports in the contiguous U.S., Alaska, Hawaii, Puerto Rico, and Guam.
The FAA first authorized operators to use RTMA temperature data in 2015 through InFO 15006 and Notice N 8900.305. In 2024, InFO 24001 superseded the original guidance and expanded RTMA’s scope to include altimeter setting data alongside temperature.
What Changed in the Latest Revision
The new guidance revises the requirements for how operators access and apply RTMA data during automated sensor failures. While the full AIN report on the revision was published on May 11, 2026, the key changes build on the 2024 update and respond to practical issues operators have raised.
Several areas have been refined over the RTMA’s evolution:
Accuracy mitigations are built in. The RTMA values aren’t used raw. The FAA requires operators to add 4°C to the RTMA-derived temperature and increase the altimeter setting by a specified margin to account for variability. These buffers ensure the data remains conservative enough for safe operations even when conditions at the actual airport differ slightly from the model’s estimate.
Landing minimums are increased. When using RTMA data in place of actual sensor readings, operators must apply higher approach minimums to account for the reduced precision compared to a direct sensor observation.
Training is required. Operators must ensure that pilots, dispatchers, and relevant operations personnel are trained on how to access and use RTMA data. The procedures need to be documented in the airline’s General Operations Manual or Enhanced Weather Information System program.
Dispatcher responsibilities are specific. For Part 121 domestic and flag operations, dispatchers must directly provide the pilot-in-command with RTMA data any time temperature or altimeter sensors fail. The RTMA report must be included in or attached to the dispatch release. For supplemental operations, the responsibility falls on the PIC.
Part 135 operators have broader access. For Part 135 operations at airports without weather reporting facilities, operators can use RTMA data even when there was never an automated system to fail in the first place — a useful provision for smaller airports.
Why This Matters for Pilots and Flight Schools
For airline and charter pilots, the practical impact is straightforward: fewer unnecessary delays when a sensor goes down at your destination or alternate. Before RTMA existed, a single failed temperature sensor could ground flights at an otherwise operational airport for hours.
For flight training, the RTMA is worth understanding for two reasons.
First, it’s a real-world example of how the National Airspace System handles sensor failures — a topic that comes up in instrument training and dispatch coursework. Student pilots and CFIs should understand the difference between ASOS, AWOS, and alternative data sources like RTMA, and when each one takes precedence.
Second, the RTMA illustrates a broader trend in aviation weather: the shift toward model-based and analysis-driven weather products that supplement traditional observation networks. NOAA’s new Domestic Aviation Forecast System (DAFS), which launched in late March 2026, is another example. DAFS uses NOAA’s High-Resolution Rapid Refresh (HRRR) model to provide higher-resolution icing and turbulence forecasts than were previously available.
Where to Access RTMA Data
RTMA reports are available online through NOAA’s Environmental Modeling Center. Each report shows the station identifier, latitude/longitude, temperature in Celsius, and altimeter setting for covered airports, updated every hour.
One important detail: the data is web-based only. There’s no integration into avionics or EFB systems yet. The FAA notes that operators should refresh their browser or clear their cache to ensure they’re viewing the most current data — a quirk of the system’s web-only delivery.
The FAA is also developing a Surface Weather Status Dashboard, proposed in a May 2026 Federal Register notice, that would let pilots, meteorologists, and the public report issues with ASOS and AWOS stations. The dashboard would track outages and erroneous data across the system and display real-time service status — a welcome addition that could make it much easier to know when RTMA is needed.
