Boeing 737 MAX: Structural Severity Backtest
Four Frequencies Framework | 2013–2024 | NTSB, FAA, SEC Data
How to Read This Chart
The Four Frequencies
Each line on this chart represents one of the Four Frequencies, scored from 0 (healthy) to 1 (critical). Permission measures the gap between what an organization is allowed to do and how effectively anyone checks that authority. Absence measures capabilities that should exist but don't: safety systems never built, risk functions left empty, testing layers skipped. Thinness measures concentration risk: how much depends on too few people, systems, or suppliers, so that losing any one causes disproportionate damage. Management measures the gap between what internal metrics report and what is structurally true. When the numbers look fine but the underlying conditions do not, this line rises.
The Composite
The thick gold line is the composite score: a weighted average of all four frequencies. The weights vary by case based on which structural dynamic dominated. A rising composite means the overall structural condition is deteriorating. A falling composite means constraints are being rebuilt. The composite does not predict when something will break. It measures how much structural strain exists when it does.
The Severity Bands
The colored background zones show severity thresholds, from dark green at the bottom (baseline health) through progressively warmer colors to dark red at the top (critical failure). When a line enters the orange-to-red zone above 0.55, that condition has moved beyond early warning into active degradation. When the composite enters that zone, multiple conditions are degrading simultaneously.
The Event Markers
Vertical dashed lines mark real-world events: crashes, regulatory changes, leadership departures, failures. The chart does not cause these events. It shows what structural conditions existed when they occurred. The gap between when the framework detects escalation and when the event happens is the structural lead time: the window during which the condition was readable in the data. Hover over any data point on the chart to see its exact value.
Composite
Weighted average of all four frequencies. The thick gold line. Weights for this case are in the Methodology section below.
Permission
The gap between what an organization is allowed to do and how effectively anyone checks that authority.
Absence
Capabilities that should exist but don't: safety systems, risk functions, testing layers that were never built or were removed.
Thinness
Concentration risk: how much depends on too few people, systems, or suppliers, making the organization fragile to single points of failure.
Management
The gap between what internal metrics report and what is structurally true. When the numbers look fine but the underlying conditions do not.
Severity:
0–0.25 Baseline
0.25–0.40 Low
0.40–0.55 Moderate
0.55–0.70 High
0.70–0.85 Severe
0.85–1.0 Critical
Boeing Was Allowed to Certify Its Own Safety, and the Framework Tracked What Happened Next
In 2005, one FAA safety engineer oversaw roughly every 63 Boeing employees doing certification work. By 2019, that ratio had barely changed. But the scope of what Boeing was certifying on its own kept growing. MCAS, the flight control system at the center of both crashes, was originally a minor addition. By final design it could push the nose down based on a single sensor with no pilot override. That expansion happened inside Boeing's own approval process, with no FAA reassessment. The Permission signal catches this: it rises from 0.20 in 2013 to 0.85 in 2019 as the gap between what Boeing was allowed to do and what anyone was checking kept widening.
Each Failing Frequency Made the Next One Worse
Weakened oversight (Permission) meant safety gaps went undetected (Absence). Those gaps got locked into a design that concentrated risk on a single sensor (Thinness). And internal metrics kept showing everything on track (Management). The framework shows this as a sequence where each line starts climbing before the next one does. Permission leads. Absence follows. Then Thinness and Management catch up. By 2018, all four are above 0.45. That is what cascading structural failure looks like before the crashes happen.
They Partially Fixed It, Then It Broke the Same Way Again
After the two crashes, all four signals drop as Boeing and the FAA rebuild constraints. But by 2024, the Alaska Airlines door plug blowout sends everything back up. Permission reaches 0.85 again. The framework is reading the same pattern in a different part of the organization. The fragility migrated from design to manufacturing, but the structural signature is identical.
How This Connects to the Full Forensic Analysis
The chart shows a cascading sequence: Permission leads, then each frequency amplifies the next. The
full forensic analysis identifies the deeper architecture — a Permission-Management co-keystone, where weakened certification authority and corrupted internal metrics each accelerated the other. The cascade the chart tracks is the signal that paired corruption produces. Both readings are the same failure seen from different structural altitudes.
Sources: NTSB Accident Investigation Reports (Lion Air 610, Ethiopian 302); FAA OIG Report AV2021020;
House Transportation Committee Investigation (2020); Senate Commerce Committee Investigation (2020); DOJ Deferred Prosecution
Agreement (2021); SEC Enforcement Action (2022); Boeing SEC 10-K filings; FAA Safety Culture Audit (2024).
Methodology: Severity 0–1 scale. Weights: Permission 0.35 (certification authority), Absence 0.30,
Thinness 0.20, Management 0.15. See DATA-PROVENANCE.md for full classification.