About the Aviation Safety Monitor

The Aviation Safety Monitor is a service provided by Robust Analytics to deliver timely information on terminal area safety in the National Airspace System (NAS). The safety monitoring and prediction technologies were developed by Robust Analytics over the past several years. Partial funding was provided by the NASA Small Business Innovation Research Program and the NASA System Wide Safety Project.

The Aviation Safety Monitor provides quantitative estimates of safety margins at 26 airports in 17 metropolitan regions in the United States. This information complements data on several safety-related events that are published elsewhere, with the FAA’s Runway Incursion Statistics website a good example. However, the available safety information can be misleading if it only reports the frequency of violations with no insight into how safety buffers may vary minute-to-minute and day-to-day. The Aviation Safety Monitor aims to provide this insight every week.

How Do We Measure Safety Margins?

The Aviation Safety Monitor summarizes output from Risk Tracker, the Robust Analytics in-time terminal airspace hazard and safety metrics monitoring system.

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Aviation Safety Monitor Weekly Report for the Week Ending February 8, 2025

There was little change in terminal airspace safety margins last week as they remain at their degraded levels of the past several months. Mean daily encroachment durations for February are 5.6 percent above the January average. The metrics are better than the December peak but February is the third worst month since started reporting in March 2024. The February daily encroachment average is 64 percent above the value for May 2024.

Weekly Safety Margin Update. Every Monday Robust Analytics reports on safety margins at 26 United States airports. With this Aviation Safety Monitor Weekly Report, Robust Analytics offers the aviation community timely assessments of changing safety margins and safety-related events. Dates and times are tracked in UTC and the week ends at midnight every Saturday. This week’s report includes data through 2400 UTC on February 8, 2025.

For New Readers: Please read our article “Did Safety Degrade in the National Airspace System in the Winter of 2022-2023?” that applies our methods and data to examine whether safety margins decreased during the events of winter 2022-2023.

The Aviation Safety Monitor measures safety margins by estimating the frequency, duration, and severity of buffer encroachments. Our paper “How Do We Measure Safety Margins?” provides a detailed description of the methods and data. That article can be found here https://www.robust-analytics.com/measure on the Robust Analytics website.

The Weekly Safety Report uses buffer encroachment events and durations to measure changes in safety margins. With this week’s update, buffer encroachment duration metrics are back to the levels of September, before the big increases in November and December. Total encroachment durations for the week decreased 4.1 percent and the number of encroachment events dropped 7.2 percent. A welcome improvement after increases the previous two weeks.

Figure 1. Weekly Buffer Encroachment Metrics

This week we continue reporting buffer encroachment durations by separation conformance category. This added detail is more informative to readers, as the Category PE and C buffer encroachments are strongly affected by meteorological conditions. In fact, by definition, during visual meteorological conditions there are no buffer encroachments. The more severe encroachments in Category A and B provide a better indicator of changing safety margins.

Figure 2 reports the weekly total durations for the two conformance category groupings.

The Category PE and C weekly durations bounce around with little long-term trend since we started reporting in February, primarily reflecting week-to-week variations in meteorological conditions. Last week the PE and C buffer encroachment durations rose 60 percent, while Category A and B duration totals for the week ending February 8 decreased 11 percent from the previous week. The metric is 47 percent above the low recorded in the first week of May.

Figure 2. Weekly Trends in Encroachment Durations By Separation Conformance Category

Figure 3 reports the 24-hour moving average encroachment duration per aircraft of all conformance categories since February 2024. Figure 3 also indicates the historical range of the data by showing the 25th, 75th, and 90th percentile values of the duration per aircraft metric. The percentiles were estimated using data from May 2022 through February 2024.

This metric returned to its range from September and October, but with higher variance, and remains similar to February and March of 2024. Seasonal patterns appear to be persistent and we will continue to analyze the historical data to identify recurring patterns.

Figure 3. Moving Average Hourly Encroachment Duration Per Aircraft From February 18, 2024 Through February 8, 2025