NTSB: Misplaced Wire Label Triggered Blackouts on Cargo Ship Dali, Causing Key Bridge Collision and Collapse

Summary

The National Transportation Safety Board (NTSB) concluded that a small identification label placed incorrectly on a signal wire during the construction of the container ship Dali likely initiated a cascade of electrical failures that led the vessel to strike the Francis Scott Key Bridge on March 26, 2024. The impact caused the bridge’s collapse and six fatalities. Investigators say preventable equipment and oversight failures, and an unassessed bridge vulnerability, combined to produce the tragedy.

What the NTSB found

Label caused poor connection: The NTSB reported that a sticker identifying a signal wire was installed in the wrong position when the ship was built. The label interfered with the wire seating properly in a circuit breaker, producing a poor electrical connection that triggered the initial blackout.

Sequence of failures: According to Marcel Muse, the NTSB investigator in charge, the first outage lasted 58 seconds and knocked out steering, the bow thruster, critical pumps and most vessel lighting and operational systems. Crew members quickly found the tripped breaker and restored power within 58 seconds.

However, a pump that should have automatically supplied fuel to the ship’s generators did not restart automatically and required manual intervention, which was not completed. As fuel lines to the generators ran dry, the ship experienced a second blackout. At that moment the Dali was about three ship lengths from the Key Bridge; despite pilots responding correctly, the vessel could not be controlled in time to avoid collision.

Earlier problems: Roughly 10 hours earlier, while moored, the Dali had experienced two onboard blackouts, one attributed by investigators to crew error.

“The fact is, none of us should be here today,” NTSB Chair Jennifer Homendy said. “This tragedy should have never occurred. Lives should have never been lost — as with all accidents we investigate, this was preventable.”

Bridge vulnerability and broader risks

The NTSB found the Key Bridge carried nearly 30 times the acceptable collapse risk for critical bridges if struck, using guidance from the American Association of State Highway and Transportation Officials (AASHTO). That risk had not been identified because the bridge owner, the Maryland Transportation Authority (MDTA), had not performed a vulnerability assessment.

The NTSB also identified 68 other bridges in 19 states that span waterways used by large cargo ships, were built before 1991, and currently lack vulnerability assessments. The list includes major crossings such as the Golden Gate Bridge (CA); Brooklyn, Manhattan, Williamsburg, George Washington and Verrazzano-Narrows bridges (NYC); the Walt Whitman and Benjamin Franklin bridges (PA); Sunshine Skyway (FL); and the Mackinac Bridge (MI).

Costs, timeline and next steps

The Maryland Transportation Authority said the updated estimate to replace the Key Bridge is $4.3 billion to $5.2 billion, with the new span now expected to open in late 2030 — about two years later than previously projected. That figure is more than double earlier estimates of $1.7 billion to $1.9 billion.

The NTSB held a public meeting to present findings and at the close of the session the board planned to vote to determine the probable cause and approve a final accident report.

Sources and attribution

This report summarizes findings released by the NTSB and reporting by CNN. Michelle Watson contributed to the original news coverage.