(new: more details)

WASHINGTON (dpa-AFX) - "Delayed" flashed on display boards at airports across the United States Wednesday morning (local time). Planes were not allowed to take off after the U.S. Federal Aviation Administration (FAA) grounded planes on all domestic routes. The reason was a computer glitch at the FAA, which according to the authority had already occurred on Tuesday evening. It was not initially known how this occurred. There were no signs of a cyber attack at the moment, the White House said. Thousands of travelers across the country had to wait. There had not been such a flight ban since the terrorist attacks of September 11, 2001 in the United States.

Affected was a system that provides pilots and other flight personnel with important safety information and notifications about disruptions in flight operations. The first news of the glitch surfaced early Wednesday morning as airline passengers across the country were already waiting at check-in desks. The grounding also caught some while they were already on the plane.

By 10:15 a.m. local time in Washington (4:15 p.m. CET), nearly 5,800 flights had been delayed and more than 950 had been canceled, according to the website Flightaware. Although the grounding of domestic flights had already been lifted shortly before 9:00 a.m., the delays would continue throughout the day, according to the airlines, the news channel CNN reported.

The reason for the glitch was still unknown Wednesday morning, according to the FAA. "We continue to search for the cause of the problem," the FAA reported on Twitter. U.S. President Joe Biden said he was in contact with Transportation Secretary Pete Buttigieg and would be kept updated on the situation. Buttigieg wrote on Twitter that he had ordered an investigation into the outage.

Lufthansa said the disruption did not affect flights to and from the United States. The breakdown in the U.S. also had no impact on Germany's largest airport in Frankfurt, according to Fraport.

After the breakdown, questions were raised about how well U.S. air traffic is prepared for incidents. It was only over Christmas that the airline Southwest had to cancel more than 16,000 flights following a massive cold snap. According to analysts, it was not only the weather that was responsible, but above all an outdated computer system, as reported by the radio station NPR. According to the airline, the outages could have caused financial damage of up to 825 million U.S. dollars (about 770 million euros). Details of the current incident are not yet available./htg/DP/nas