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 15, 2025

Safety margins fell sharply last week, dropping to the lowest level since we began publishing the Aviation Safety Monitor one year ago. The seasonal pattern for the previous two winters saw safety margins decline from September to December but then begin to improve steadily through the summer. That pattern is not holding this year, as safety margins remain stubbornly low this month. Mean daily encroachment durations for February are 30 percent above the January average and increasing. The metrics are slightly better than the December peak but February is the second worst month over the past year. The February daily encroachment average is 2.1 times greater than the low value from 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 15, 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. The safety trend is strongly negative this month. Total encroachment durations increased three out of the past four weeks and are now at the highest weekly level reported over the past twelve months. Total encroachments durations for the week were 45 percent higher and the number of events jumped 30 percent. Safety margins are clearly degrading, when we would expect gradual improvement at this time of the year based on historical seasonal patterns. We are not observing those improved safety margins in 2025.

Figure 1. Weekly Buffer Encroachment Metrics

Buffer encroachments are classified into four separation conformance categories based on the severity of separation deviation. Category PE and C buffer encroachments identify relatively weak separation conformance deviations and 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 80 percent, while Category A and B duration totals for the week ending February 15 increased 26 percent from the previous week. The combined metrics increased 45 percent last week and was 2.7 times greater than 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.

Figure 3. Moving Average Hourly Encroachment Duration Per Aircraft From February 18, 2024 Through February 15, 2025

Figure 3 reports data for past twelve months and the pattern is very clear. The historical pattern of increasing buffer encroachments from the summer low into winter held, but we are not seeing the improvement expected in January and February. Variance is also higher with many more disturbingly high encroachment periods. It is time to conduct a deep dive into the data and determine why safety margins remain degraded. We will conduct that study and report the findings in a Special Report by the Aviation Safety Monitor research team.