Aviation Safety Monitor Weekly Report for the Week Ending March 1, 2025

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Safety margins remain degraded this week, even worsening in some of the key risk metrics. This situation offers an opportunity to examine the data from  the past twelve months and review what is happening in the world of aviation safety. The short summary: the situation is not good. The risk metrics show clearly that safety margins have decreased significantly over the past twelve months. The mean daily encroachment duration for February 2025 is 60 percent above the March 2024 estimate. Based on analysis of previous years, we expect encroachment durations to peak in December, then gradually decline through the summer months. Unfortunately, this year the mean February encroachment duration was 27 percent above the January estimate, suggesting that conditions are deteriorating rather than improving. The data suggest that the NAS is showing signs of stress similar to the winter of 2022-2023, and the recent incidents may be indicators of that degradation in safety margins.

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Figure 1. Mean Daily Encroachment Durations By Month

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 March 1, 2025.  

 

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​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. Safety margins remained low last week, as the risk metrics continue to send mixed signals the past few weeks. Total encroachment durations increased by six percent, while the number of encroachment events dropped 15.6 percent. This continues the increase in duration per encroachment event over the past month, which jumped 10.6 seconds  – a 47 percent increase in just four weeks. The more severe Category A and B separation conformance deviations rose by 22 percent and last week’s metrics are the highest recorded in the past twelve months. 

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The NAS is simply not showing the improvements in safety margins that we expect at this time of the year. 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 were 27.3 percent above the January average. Those metrics are slightly better than the December peak but February 2025 was the second worst month over the past year. The February daily encroachment average is two times greater than the low value from June 2024.

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 2. 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 3 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 and some seasonal variation. Last week the PE and C buffer encroachment durations dropped more than sixty percent, but that was from the highest level reported since we began reporting 12 months ago. Category A and B duration totals for the week ending March 1 increased 6.2 percent from the previous week. The combined metrics are 2.1 times greater than the low recorded in the first week of May. 

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Figure 3. Weekly Trends in Encroachment Durations By Separation Conformance Category

Figure 4 reports the 24-hour moving average encroachment duration per aircraft of all conformance categories since February 2024. Figure 4 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.

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Figure 4. Moving Average Hourly Encroachment Duration Per Aircraft From February 18, 2024 Through March 1, 2025

Figure 4 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. Expect to see those findings soon in a Special Report by the Aviation Safety Monitor research team.