The 984-foot-long ship lost steering and propulsion due to blackout.
WASHINGTON (Nov. 18, 2025) – A loose wire on the 984-foot-long containership dock caused an electrical blackout, causing the massive vessel to turn and contact the nearby Francis Scott Key Bridge in Baltimore, the NTSB said Tuesday, before collapsing, killing six highway workers.
At a Tuesday public meeting at NTSB headquarters, investigators said a loose wire in the ship’s electrical system caused a breaker to open unexpectedly — setting off a sequence of events that led to two ship blackouts and the loss of both propulsion and steering near the 2.37-mile-long Key Bridge on March 26, 2024. The investigators found that the wire-label banding prevented the wire from being fully inserted into the terminal block spring-clamp gate, causing an inadequate connection.
The illustration shows how the location of the wire-label banding affects the way the wires sit in their terminal blocks. (Source: NTSB)
After the initial blackout, the direction of the cast began to swing to starboard toward the bridge’s Pier 17. Investigators found that the pilots and bridge team attempted to alter the ship’s trajectory, but the loss of propulsion so close to the bridge made their actions ineffective. A large section of the bridge subsequently fell into the river, and parts of the pier, deck and truss spans fell onto the ship’s bow and foremast container bays.
A seven-man road maintenance crew and an inspector were on the bridge when the ship was attacked. Six highway workers died. The NTSB found that the prompt actions of cast pilots, shoreside dispatchers, and the Maryland Transportation Authority to stop bridge traffic prevented greater loss of life.
“Our investigators routinely accomplish the impossible, and this investigation is no different,” said NTSB Chair Jennifer Homendy. “The branch, at an altitude of nearly 1,000 feet, is as tall as the Eiffel Tower, with miles of wiring and thousands of electrical connections. Finding this single wire was like looking for a loose rivet on the Eiffel Tower.
“But like all crashes we investigate, this could have been prevented,” Homendy said. “Implementing the NTSB’s recommendations in this investigation will prevent similar tragedies in the future.”
A factor contributing to the Key Bridge collapse and loss of life was the lack of measures to reduce the risk of bridge collapse due to impact from ocean-going ships, which has grown larger since the Key Bridge opened in 1977. When the Japan-flagged containership Blue Nagoya approached the Key Bridge after losing propulsion in 1980, the 390-foot-long ship sustained only minor damage. However, Dali Blue is 10 times larger than Nagoya.
Comparative size of Blue Nagoya and Dali relative to Key Bridge. (Source: NTSB)
As part of the investigation, the NTSB released a preliminary report in March on the vulnerability of bridges across the country to strikes by large ships. The report found that the Maryland Transportation Authority – and many other owners of bridges spanning navigable waterways used by ocean-going vessels – were unaware of the potential danger that ship collisions could pose to their structures. This was despite long-standing guidance from the American Association of State Highway and Transportation Officials recommending that bridge owners conduct these assessments.
The NTSB sent letters to 30 bridge owners identified in the report urging them to evaluate their bridges and, if necessary, develop plans to reduce risks. All recipients have since responded, and the status of each recommendation is available on the NTSB’s website.
As a result of the investigation, the NTSB issued new safety recommendations to the US Coast Guard; US Federal Highway Administration; American Association of State Highway and Transportation Officials; Nippon Kaiji Kyokai (ClassNK); American National Standards Institute; American National Standards Institute Accredited Standards Committee A10 on Safety in Construction and Demolition Operations; HD Hyundai Heavy Industries; Synergy Marine Pte. Ltd; and WAGO Corporation, electrical component manufacturer; and many bridge owners across the country.
A summary of the actions taken Tuesday, including probable cause, findings and recommendations, can be found at ntsb.gov. The full investigation report will be released in the coming weeks.
To report an incident/accident or if you are a public safety agency, please call 1-844-373-9922 or 202-314-6290 to speak to a watch officer at the NTSB Response Operations Center (ROC) in Washington, DC (24/7).