Simon Carswell, Washington Correspondent
Trading on the New York Stock Exchange came to a halt on Wednesday morning due to a technical fault, just hours after a computer glitch grounded all of United Airlines flights in the United States.
The stock exchange stopped trading at about 11.32am local time (4.30pm in Ireland), forcing traders to place orders on some of the country’s 10 other exchanges or more than 50 private markets where American shares are traded.
Market trading resumed in the late afternoon, almost four hours after the stoppage began and less than an hour before the 4pm closing bell.
Management at the Wall Street bourse said there was no sign of a cyber attack by outside hackers, blaming the stoppage on a technical problem.
“The issue we are experiencing is an internal technical issue and is not the result of a cyber breach,” the exchange said in a message posted on social media website Twitter.
“We chose to suspend trading on [the] NYSE to avoid problems arising from our technical issue.”
Shortly after 8am, the exchange had issued an alert about “a reported issue with a gateway connection” that was affecting certain stocks. It put out a follow-up alert at 10.37am saying that this issue had been resolved before the exchange later suspended all trading.
President Barack Obama along with White House and US treasury officials were briefed about the stoppage and were monitoring the situation, White House press secretary Josh Earnest said.
There was “no indication that malicious actors were involved”, he said.
The FBI said that it would “monitor the situation” but “no law enforcement action is needed at this time”.
US Securities and Exchange Commission chairwoman May Jo White said in a statement that it was “in contact with the NYSE and are closely monitoring the situation”.
The shutdown on the New York bourse, the world’s largest exchange based on the value of the shares on the market, is the biggest disruption to an American stock trading venue in almost two years.
The glitch did not appear to be connected to an earlier computer problem at United Airlines, according to US officials quoted in the US media. About 4,900 flights were affected by the problem worldwide.
The home page of the Wall Street Journal's website was also affected by an outrage on Wednesday in the unusual series of technical problems.
The Federal Aviation Administration issued a ground stop at 8.26am (1.26pm Irish time) blocking all United flights from taking off. The stop was not lifted for all of the company’s aircraft until 9.47am.
Flights resumed mid-morning but the grounding of planes led to knock-on delays at airports across the country. The airline issued a statement saying that it had suffered from “a network connectivity issue this morning” and apologised to customers for the inconvenience caused to their travel plans.
“There was no hacking whatsoever,” an airline official told news channel CNN.
Washington DC-based journalist Betsy Fischer Martin, who was delayed on a grounded flight, tweeted that the pilot on her plane addressed passengers, telling them: “It’s like someone pulled the plug on our computers – it’s embarrassing; I apologise.”
US security officials were quick to quell concerns that the companies were the victims of a co-ordinated cyberattack. Homeland Security secretary Jeh Johnson said that the “malfunctions” at United Airlines and the New York Stock Exchange were “not the result of any nefarious actor”.
