A sweeping technology outage forced United Airlines to ground flights across the US, causing widespread delays and cancellations that affected thousands of passengers – including many from the Indian diaspora flying home for weddings, family visits, or returning to work after summer.

The glitch, traced to the airline’s aging Unimatic system used for flight dispatch and load planning, brought operations at major hubs to a halt for several hours on Wednesday.

The Federal Aviation Administration (FAA) confirmed that United requested a nationwide ground stop, which has since been lifted, but delays were still rippling across the network on Thursday.

United called it a “controllable delay”, pledging to cover hotels and related costs where needed, and emphasized that the outage was not cybersecurity-related.

“Safety is our top priority, and we’ll work with our customers to get them to their destinations,” the airline said in a statement.

FlightAware, a website tracking flight disruptions, reported that about 35 per cent of all the airline’s flights were delayed and 7 per cent were cancelled Wednesday.

United’s travel alert warned of disruptions through the weekend at key US and international airports including Newark, Houston, Chicago, Washington, Los Angeles, San Francisco, Denver, Orlando, New York, Honolulu, Guam, London, Frankfurt and Munich.

Among those impacted was Ishya K, a young consultant, originally from Houston, and now working in Manhattan, who had flown over the weekend to visit her family. Her evening flight to New York’s LaGuardia (LGA) was first delayed for hours and then abruptly cancelled just before midnight.

“There was so much chaos at the airport as United didn’t know what was going on.They finally told us around 11 pm that we weren’t flying out,” she said. “I reached home past midnight after hours at the airport, and now I’ve been rebooked for a late flight today and hope there are no more delays.”

Others missed international connections altogether. Michael Tran, who was headed to Japan from Houston via San Francisco, was stranded overnight and unsure whether he’d make it in time for a long-planned trip.

For the Indian-American community, peak summer travel collided with deeply personal commitments. Nisha Mehra, a professional, originally from Delhi, missed her flight to India – and with it, the first wedding in her family she would have attended in a decade.

“This was my chance to reconnect with my family in Chandigarh after so many years,” she said, tearing up at the terminal. “I had my bags packed with gifts for all the cousins. Now I’m hoping I can get there before the last event.”

Passengers across the country described hours inside aircraft after landing, waiting for gates to open due to a system-wide standstill. “The first hour, people were already walking around the cabin because there was nothing to do,” said one passenger. “Eventually they found a gate, but it still took another 45 minutes to get there.”

The FAA said it continues to assist United in resolving the backlog. “We’ve offered full support to help address their flight backlog and remain in close contact,” the agency said.

United apologised publicly via social media. “Hey there, we apologise for the travel disruption today,” it said in response to customer complaints. “Our teams are working to resolve the outage as quickly as possible.”

While operations are slowly resuming, United warned that passengers flying in or out of affected cities may continue to face delays.