Failure pattern · United States · 2024
CrowdStrike 2024: one update crashes 8.5 million computers
A faulty content update to CrowdStrike's security software crashed about 8.5 million Windows devices worldwide, grounding flights and disrupting hospitals, banks, and broadcasters.
By Shivam Bhandari · Reviewed 31 October 2026 · How we write
by the numbers
- Devices affected
- about 8.5 million
- Date
- 19 July 2024
- Delta's estimated losses
- about $500 million
What happened
CrowdStrike's Falcon software protects business computers against cyberattacks and runs deep inside the Windows operating system. On 19 July 2024 it pushed a routine configuration update to customers worldwide.
The update contained an error that caused Windows computers to crash and fail to restart. Microsoft estimated about 8.5 million devices were affected. Airlines grounded flights, hospitals postponed procedures, and banks and broadcasters went offline. Many machines had to be fixed manually, one by one.
CrowdStrike apologised, published a root-cause analysis, and committed to staged rollouts so updates reach small groups first. Delta Air Lines said the outage cost it about $500 million and pursued legal action.
Timeline
- 2024
Faulty update (July 19); root-cause report; staged rollouts introduced.
what went wrong
- Update pushed to all customers at once.
- Software ran at a deep level where errors crash the whole system.
- Testing failed to catch a malformed file.
the lesson
Releasing changes to everyone at once turns a small mistake into a global disaster — roll out gradually.
Apply it to your business
- 1Roll out changes to a small group first.
- 2Have a fast rollback plan for every release.
- 3Know which suppliers are single points of failure for you.
Laws at work in this story
Figures are rounded and drawn from public reports, company filings and widely cited coverage at the time. Check the company's latest filings before relying on any number.