Key Points
- More than 6,000 flights were delayed and nearly 1,000 cancelled.
- The number of flights affected rose even after the ground stop was cancelled.
- US President Joe Biden ordered the Transportation Department to investigate.
United States flights are slowly resuming departures and a ground stop has been lifted after the Federal Aviation Administration scrambled to fix a system outage that had forced a halt to all departing flights.
More than 6,000 flights were delayed and nearly 1,000 cancelled according to the FlightAware website as officials said it will take hours to recover from the halt. The numbers were still rising.
The cause of the problem with a pilot-alerting system was unclear, but US officials said they had so far found no evidence of a cyber attack.
The outage occurred at a typically slow time after the holiday travel season, but demand remains strong as travel continues to recover to near pre-pandemic levels.
"Normal air traffic operations are resuming gradually across the US following an overnight outage to the Notice to Air Missions system that provides safety info to flight crews. The ground stop has been lifted. We continue to look into the cause of the initial problem," the FAA tweeted.
The number of flights affected rose even after the ground stop was cancelled.
One issue airlines are facing is trying to get planes in and out of crowded gates, which is causing further delays.
At an airport in Greenville, South Carolina, Justin Kennedy abandoned a work trip to nearby Charlotte.
He said confusion reigned as airline employees were not aware what the FAA was saying, and many passengers were initially unaware of the delays.
"I sat in a Chick-fil-A dining area that had a good view of the TSA exit," the 30-year-old information technology employee said.
"I saw at least four people sprinting to gates because they thought they were going to miss their flight, only to come back to the food court, out of breath."
Thousands of flights throughout the US are gradually resuming after the Federal Aviation Administration suffered an early morning outage to the Notice to Air Mission System, a computer system that helps guide air traffic. Source: Getty / John Moore
"This thing was lifted at 9am Eastern. That doesn't mean the problem stops at 9am. This is going to cause ripple effects," said Mr Torres, whose members fly for American Airlines.
"The end result of this is going to be very similar to big weather events."
The FAA had earlier ordered airlines to pause all domestic departures after its pilot alerting system crashed and the agency had to perform a hard reset about 2am, officials said.
Flights already in the air were allowed to continue to their destinations.
US President Joe Biden ordered the Transportation Department to investigate and said the cause of the failure was unknown.
Asked if a cyber attack was behind the outage, Mr Biden told reporters, "We don't know."
Transportation Secretary Pete Buttigieg pledged a "process to determine root causes and recommend next steps".
A NOTAM is a notice containing information essential to personnel concerned with flight operations but not known far enough in advance to be publicised by other means.
A ground stop is an air traffic control measure that slows or halts aircraft at a given airport.
A total of 21,464 US flights were scheduled to depart on Wednesday with a capacity of nearly 2.9 million passengers, data from Cirium showed.
