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Case Study #98 — Top 100 Software Failures

FAA Los Angeles air traffic control system shutdown

About 3 hours of lost radio contact between controllers and aircraft over Southern California, Nevada, Arizona and Utah; hundreds of flights were delayed, diverted or cancelled, and investigators found several aircraft had come dangerously close together.

2004-09-14
When it happened
Aviation / Government
Sector
#98 of 100
Ranked by documented impact
01 — What Happened

The damage was public. The root cause was preventable.

About 3 hours of lost radio contact between controllers and aircraft over Southern California, Nevada, Arizona and Utah; hundreds of flights were delayed, diverted or cancelled, and investigators found several aircraft had come dangerously close together.

Aviation
Sector affected
2004-09-14
Date of the event
#98
Rank in the Top 100 Software Failures
3
Distinct root-cause clauses identified below
02 — The Root Cause

What the software actually got wrong

The Voice Switching and Control System's software was designed to shut itself down automatically unless a technician manually reset an internal countdown timer every 30 days; the reset was missed, and a backup system that was supposed to take over had been misconfigured and failed to activate.

01Root Cause

The Voice Switching and Control System's software was designed...

What Happened

The Voice Switching and Control System's software was designed to shut itself down automatically unless a technician manually reset an internal countdown timer every 30 days

How Requs AI Catches This

Requs AI Edge Case flags this exact pattern at the requirements and architecture stage — before a single line of code implementing it exists — so the assumption behind it gets challenged while it is still cheap to fix.

02Root Cause

The reset was missed

What Happened

the reset was missed

How Requs AI Catches This

Requs AI Software FMEA traces this failure mode back to the system-level hazard it feeds, tagging it against the Common Defect Enumeration so it surfaces in review instead of in the field.

03Root Cause

A backup system that was supposed to take over...

What Happened

a backup system that was supposed to take over had been misconfigured and failed to activate

How Requs AI Catches This

Requs AI Edge Case and Software FMEA together treat this as a known, catalogued defect pattern — not a novel surprise — so it gets tested for deliberately rather than discovered after deployment.

03 — How This Gets Caught Before It Happens

Beyond code coverage and "shall" testing

Root causes like this one rarely show up in code coverage or requirements-compliance testing, because nobody wrote a requirement anticipating the specific edge case that broke. Requs AI Edge Case and Requs AI Software FMEA are built to surface exactly this class of overlooked failure mode — before the software is written.

Requs AI Edge Case

Surfaces this before code exists

Identifies edge cases like this one at requirements and architecture time, using the Common Defect Enumeration to catalog failure patterns seen across hundreds of real-world software failures — including this one.

Requs AI Software FMEA

Connects the failure mode to the hazard

Traces this class of root cause directly to the system-level hazard it can produce, so a defect pattern like this one gets flagged during design review instead of after it ships.

Find the overlooked root causes before they ship.

Schedule a demonstration, or explore how Requs AI Edge Case and Software FMEA use the Common Defect Enumeration.