One loose wire caused ship blackout that toppled the Key Bridge, took six lives, NTSB says

That was the focus of a daylong hearing Tuesday by the National Transportation Safety Board, which also reported that protective barriers on the 50-year-old Key Bridge were no match for the size of modern cargo ships. The NTSB also said that workers on the bridge might have been able to escape, but no one called them to warn them of the impending crash.

Bridge police were called 1 minute, 29 seconds before the crash, giving them enough time to close the bridge to traffic and save lives in the process, according to the NTSB investigation.

The workers were sitting in their vehicles on break at the time. Had they been alerted at the same time as the police, it still would have been an incredibly tight window get clear of the bridge — one worker was parked a little more than a half-mile from safety — but that phone call was not made, said the board.

Two other crew members survived the collapse: An inspector who fled the falling spans on foot and a worker who escaped his vehicle after it plunged into the Patapsco River.

Much of Tuesday’s meeting, however, focused on the mechanical failures on the 984-foot-long cargo ship, Dali, as it lost power and veered toward the Key Bridge in the middle of that cold March night. The failures occurred so close to the bridge that scrambling crew members, who responded as efficiently as possible, did not have time to prevent disaster, according to the board’s findings.

NTSB investigators traced the blackout to a single wire with a misplaced label, which created a precarious electrical connection that allowed the wire to disconnect from its terminal block and plunge the ship into darkness.

“Locating a single wire that is loose among thousands of wires is like looking for a loose bolt in the Eiffel Tower,” said Board Chair Jennifer Homendy, who applauded the work of investigators.

Among a host of safety recommendations for governments, businesses and others, the board said Hyundai Heavy Industries and other ship builders should ensure that wire labels are installed correctly, preventing wires from becoming dislodged. Board staff also recommended that ship inspectors use a technology called thermography, which could have detected the wiring issue in advance of the crash.

The Dali also had a loss of power in port a day before the crash, but that blackout was unrelated to the power outage a day later that led to the bridge collapse, according to the NTSB. A crew member working on the ship “inadvertently closed” an exhaust mechanism, causing the engine to sputter, said the NTSB’s Barton Barnum.

“It was all rather, rather obvious, OK, he knew immediately that his actions had caused the engine to disconnect and black out the vessel,” Barnum said.

NTSB staffers said Tuesday that they do not think the ship’s crew was under any obligation to report that power loss to the pilots who would guide the Dali out of the Seagirt Marine Terminal, because they had no reason to believe it had compromised the ship.

In addition to the mislabeled wire, other key pieces of equipment aboard the ship were set up incorrectly and unable to handle the power loss, investigators said.

Aboard the Dali, a fuel flushing pump was improperly installed as a fuel oil service pump, serving two diesel generators. When the ship lost power, that pump could not automatically restart. So once the ship briefly came back online, those diesel generators were starved of fuel, causing the second blackout.

The NTSB believes that the improper configuration had been in place on the Dali for at least seven months, because the normal pump system was believed to be contaminated.

“In order for them to use that system, it would need to be opened up and cleaned, a process that would take a couple days. So they opted to continue using the flushing pump,” Barnum said.

The ship’s owner, Synergy Marine, should have discovered the improper setup based on email reports coming from the ship and addressed the problem, according to the board.

Several board members expressed concern that new emissions reduction standards might have been part of the reason for the impermissible flushing pump hookup.

“I’m certainly supportive of strengthening environmental regulations,” Homendy said. “But we have to also look at safety impacts, and make sure there are not unintended consequences by use of some other configuration to comply with those emissions standards.”

But the perfect storm of events leading to the collapse also included “woefully inadequate” infrastructure protecting the Key Bridge, said Dan Walsh of the NTSB.

The bridge had 25-foot-diameter concrete “dolphins,” structures meant to prevent impacts to the bridge’s piers. But modern container ships have dramatically increased in size and capacity, and small dolphins are incapable of slowing them. Not to mention the fact that the Dali did not come into contact with any of the four dolphins around the Key Bridge, the board found.

By comparison, the Delaware Memorial Bridge has 80-foot-diameter dolphins, which are capable of puncturing the hull of even a large container ship before it strikes a pier.

Though it was not legally required to do so, the Maryland Transportation Authority failed to conduct a study of the bridge’s vulnerability to ship strikes, which would have revealed that the bridge was nearly 30 times above the acceptable risk standard.

In March 2025, the NTSB released urgent recommendations for 68 bridge owners across the nation who had not conducted that analysis to do so as soon as possible.

Some but not all of the bridge owners have since completed those studies, and bridges in New Jersey and Ohio, along with several in Louisiana are above the acceptable risk threshold. So, too, are both spans of Maryland’s Chesapeake Bay Bridge.

In its statement Tuesday, the MdTA also defended the Bay Bridge, adding that it meets federal permitting requirements, and has passed its inspections. But the agency noted that it is undertaking a $177 million project to design more protection for the critical spans, the only bay crossings that connect Maryland’s Eastern Shore to the rest of the state

“MDTA has taken steps to enhance the Bay Bridge’s physical protections because, although vessels have increased in size, weight, and speed, maritime regulations have not kept pace with the changes,” the statement reads.

Homendy took issue Tuesday with inaccuracies that she cited in the MdTA filing to the NTSB. She said she was “disappointed” that the state agency violated NTSB regulations by relying on items from discovery in its lawsuits against the companies operating the ship.

That filing referenced an “unlicensed” electrician working on the ship, Homendy said, but the NTSB found no evidence of certification issues with the mariners on the Dali.

“He was a credentialed marine electrician,” Barnum said. “He worked under the guidance of senior engineering officers, including the chief engineer.”

Maryland’s filing also argued that the blackouts in port on March 25, 2024, should have been reported on a “pilot card” for the mariners who would guide the Dali past the Key Bridge. NTSB staff disagreed.

Maryland’s filing also implied that dropping anchor could have stopped the crash, Homendy said. But NTSB staff members also disagreed on that point.

“It takes a long time to deploy an anchor that size,” said the NTSB’s Capt. Marcel Muise, adding that the speed of the vessel means the anchor would have been unlikely to prevent the crash into the Key Bridge.

The Maryland Transportation Authority did not reference the concerns about its filing in its statement, and did not respond to questions on the subject from Maryland Matters.

Homendy closed Tuesday’s briefing by emphasizing the importance of the board’s “meticulous” and lengthy study of the crash, especially when it came to the wiring on the Dali.

“We all too often get pushed in the early stages of an investigation — in fact, while we are still on scene — to determine the cause of an accident,” Homendy said. “Our investigations take time. Our findings in this investigation are a perfect example of why.”

“We all too often get pushed in the early stages of an investigation — in fact, while we are still on scene — to determine the cause of an accident,” Homendy said. “Our investigations take time. Our findings in this investigation are a perfect example of why.”

Maryland Matters is part of States Newsroom, a nonprofit news network supported by grants and a coalition of donors as a 501c(3) public charity. Maryland Matters maintains editorial independence. Contact Editor Steve Crane for questions: editor@marylandmatters.org.