In an instant, a large section of the Francis Scott Key Bridge was gone – as dozens of its steel beams collapsed into the water after being hit by a cargo ship.
Emergency services are still at the scene and details about casualties are still emerging.
Sky News has spoken to a number of maritime and engineering experts to try and understand what might have happened – and what issues may have been at play.
Image: The Singapore-flagged container ship ‘Dali’ after it collided with the bridge. Pic: Reuters
Was human error to blame?
Professor Helen Sampson, an expert at the Seafarers International Research Centre at Cardiff University, says the crash may have been caused by someone’s mistake.
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She told Sky News: “Was there some sort of miscommunication or misunderstanding between the pilot and the crew? Or was there a pilot error?”
The time of day when the disaster occurred – around 1.30am local time – gives rise to concerns about tiredness, she added.
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“The time makes me also wonder whether there was an element of fatigue at play…
“It’s almost always the case that we focus on human error at the individual level, it’s almost always the case that there’s a broader context which has resulted in that human error, like fatigue and the demands made on pilots or on crews.”
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‘They thought it was an earthquake’
What about a mechanical problem?
However, another maritime safety expert says the “most likely” cause of the crash was a failure in the ship’s machinery.
David McFarlane, director of Maritime Risk and Safety Consultants Ltd, told Sky News: “The first thing that springs to my mind is: was there a sudden fault with the ship’s engines or the steering gear?”
Mr McFarlane said a human error was less likely because of the number of people who would have been on duty.
“There should be no room for one-person errors because one of the other people should jump in and say ‘hang on’,” he said.
“The most likely cause of this is a failure in machinery or steering gear, but we just won’t know until the authorities have been on board. And even then, they’re unlikely to say what’s been going on for some considerable time.”
Prof Sampson said a mechanical failure with the steering gear or something similar would be the “most dramatic” explanation for what happened.
Officials have confirmed the ship that crashed into the bridge had issued a mayday call and had lost power.
Image: The remains of the bridge on top of the ship. Pic: Jim Lo Scalzo/EPA-EFE/Shutterstock
Was there a design flaw in the bridge?
Opened in 1977, the Francis Scott Key Bridge is named after the poet who wrote the words to the Star Spangled Banner, the American national anthem.
Constructed from steel, it was 1.6 miles long and not dissimilar to some bridges in the UK, one expert told Sky News.
Julian Carter, a structural and civil engineering expert, said these structures are simple in concept – but “very weak” at certain points.
“It’s what we call a continuous structure every little piece is connected to another – and unfortunately it’s a catastrophic collapse.”
Professor Barbara Rossi, an expert in engineering science at the University of Oxford, said the impacting force of the cargo ship must have been “immense” to lead to the collapse of the concrete structures underpinning the bridge.
“We should not speculate around if such huge impact forces should have been taken into account at the design stage,” she added.
There has also been discussion about whether “dolphins” (steel structures embedded in the seabed to stop or divert a ship) or artificial islands may have been inadequate.
Bridge designer Robert Benaim said: “I do not know what the arrangements were for this bridge but major bridges over shipping lanes must have substantial protection for piers or columns.”
He added: “If piers are not protected adequately then they are vulnerable to ship collision. Clearly the protection of the piers in this instance was inadequate. A pier or column of a bridge could never resist the impact of a large ship. They must be protected from collision.”
Image: The defendants hugged each other after being acquitted of the charges. Pic: Commercial Appeal/USA Today Network/AP
The 29-year-old’s death and a video of the incident – in which he cried out for his mother – sparked outrage in the US including nationwide protests and led to police reform.
Civil rights attorney Ben Crump, who represents Nichols’ family, described the verdicts as a “devastating miscarriage of justice”. In a statement, he added: “The world watched as Tyre Nichols was beaten to death by those sworn to protect and serve.”
Memphis District Attorney Steve Mulroy said he was “surprised that there wasn’t a single guilty verdict on any of the counts” including second-degree murder. He said Mr Nichols’ family “were devastated… I think they were outraged”.
Image: Former police officers Tadarrius Bean, Demetrius Haley, Justin Smith were accused of second-degree murder. Pic: Memphis Police Dept/AP
But despite the three defendants being acquitted of state charges during the trial in Memphis, they still face the prospect of years in prison after they were convicted of federal charges of witness tampering last year.
Two other former officers previously pleaded guilty in both state and federal court. Desmond Mills Jr. gave evidence as a prosecution witness, while Emmitt Martin was blamed for the majority of the violence.
Sentencing for all five officers is pending.
Image: Tyre Nichols’ death sparked street protests in January 2023 in Memphis and across the US. Pic: AP
Video evidence showed Mr Nichols was stopped in his car, yanked from his vehicle, pepper-sprayed and hit with a Taser. He broke free and ran away before the five police officers caught up with him again, and the beating took place.
Prosecutors argued that the officers used excessive, deadly force in trying to handcuff Mr Nichols and were criminally responsible for each others’ actions.
They also said the officers had a duty to intervene and stop the beating and tell medics that Mr Nichols had been hit repeatedly in the head, but they failed to do so.
The trial heard Mr Nichols suffered tears and bleeding in the brain and died from blunt force trauma.
The defence suggested Mr Nichols was on drugs, giving him the strength to fight off five strong officers, and was actively resisting arrest.
In December, the US Justice Department said a 17-month investigation showed the Memphis Police Department uses excessive force and discriminates against Black people.
The US central bank held interest rates as it said Trump tariffs have risked higher inflation and unemployment amid “so much” uncertainty.
The announcement is likely to anger President Donald Trump, who has made the taxes on imports one of his signature policies and had threatened to fire the Federal Reserve chair, Jerome Powell.
On Wednesday, the Federal Reserve, known as the Fed, held rates at 4.25%-4.5%. Unlike the UK, the US interest rate is a range to guide lenders rather than a single percentage.
It means borrowing costs have remained unchanged for Americans, something Mr Trump had wanted to reduce.
Interest rates have been raised by the Fed to bring down high inflation in the wake of Russia’s invasion of Ukraine and the supply chain crisis brought about by COVID-19 lockdowns.
Fears of inflation rising higher as tariffs make goods on US shelves costlier, and of job losses from reduced spending, led the Fed to remain cautious.
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The full effect of the tariffs is “highly uncertain”, Mr Powell said on Wednesday evening, as those announced so far have been “significantly larger” than anticipated.
Image: US Federal Reserve Chair Jerome Powell speaks during a news conference. Pic: Reuters
A 90-day pause was announced on the suite of taxes Mr Trump imposed on countries across the world, on top of the 10% base tariff, which has remained in place.
A trade war was kicked off between China as the countries escalated tariffs on each other to nearly 150%. Taxes on cars and some metals entering the US are still subject to a 25% tax.
If these tariffs remain, Mr Powell made the strongest statement yet that goods overall would become more expensive.
“If the large increases in tariffs that have been announced are sustained, they’re likely to generate a rise in inflation, a slowdown in economic growth and an increase in unemployment,” he said.
“The effects on inflation could be short-lived, reflecting a one-time shift in the price level. It is also possible that the inflationary effects could instead be more persistent,” he added.
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Trump’s tariffs: What you need to know
Uncertainty over the economic outlook also caused consumer and business sentiment to fall, “largely reflecting trade policy concerns”, Mr Powell said.
Despite Mr Trump appointing Mr Powell to the Fed chair position during his first term, the president has repeatedly spoken out against Mr Powell.
Markets rallied after Mr Trump ruled out ousting Mr Powell at the end of April.
It comes as the UK central bank, the Bank of England, is poised to cut interest rates on Thursday afternoon. The base rate is anticipated to drop to 4.25% before falling to 3.5% by the end of the year.
“We are already in active discussions with the top of the US administration on this subject,” he told MPs after an urgent question was raised on the matter in the House of Commons.
“We are working hard to establish what might be proposed, if anything, and to make sure our world beating creative industries are protected.”
He added that he is due to meet UK industry leaders on Thursday.
In a post on his social media platform Truth Social, Mr Trump said he had authorised government departments to put a 100% tariff “on any and all movies coming into our country that are produced in foreign lands”.
Shadow culture minister Stuart Andrew asked what impact assessment the government has made and whether there are any contingency plans if an exemption can’t be secured.
Image: Chris Bryant is a minister in the culture department
Mr Bryant said he is “not sure precisely what is intended” with the film tariffs as he doesn’t know “what a tariff on a service would look like”.
“Most films these days are an international collaboration of some kind and we want to maintain that,” he said.
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Film industry tariffs don’t’ make ‘great deal of sense’
He appeared to rule out retaliatory tariffs if Mr Trump follows through with his plan, saying the Labour government of 1947 introduced tariffs on US films because they thought too many were being shown in the cinema and “it didn’t go very well as a strategy”.
“The Americans simply banned exports of US films and we ended up watching Ben-Hur repeatedly in every cinema.
“The successful bit of what we did in 1947 and 1948 was that we invested in the British film production system. And that led to films like Hamlet and Kind Hearts and Coronets. I think that that’s the pattern that we still want to adopt.”
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At Prime Minister’s Questions on Wednesday, party leader Ed Davey urged Sir Keir Starmer to work with allies in Europe and in the Commonwealth to “make clear to President Trump that if he picks a fight with James Bond, Bridget Jones and Paddington Bear, he will lose”.
However, the PM said it is “not sensible or pragmatic” to choose between Europe and the US, with Downing Street still seeking to negotiate an “economic deal”with Washington that it hopes could offset some of Mr Trump’s measures.
Mr Trump said the film tariffs were necessary because other countries were “offering all sorts of incentives to draw” filmmakers and film studios away from the United States, calling the issue a “national security threat”.
But insiders have questioned whether it will be effective as the exodus of the film industry from Hollywood is mostly due to economic reasons, with other countries having lower labour costs and more expansive tax incentives.
Much of the 2023 box office smash Barbie was filmed at the Warner Bros Leavesden studios, in Hertfordshire, as was Wonka and 2022 hit The Batman, while the vast majority of James Bond films were shot at Pinewood Studios, in Buckinghamshire.
It was also unclear whether the duties will apply to films on streaming platforms as well as those that are released in cinemas.