Air New Zealand has delayed its flights from the United States to New Zealand by two hours after an air traffic control outage disrupted travel across the US, leaving passengers waiting on tarmacs and forcing hundreds of aircraft to divert.

Air New Zealand chief operations officer Kate Boyer said the airline delayed the flights as a precaution while it assessed the situation. In the other direction, the airline’s flights from New Zealand to the United States were still scheduled to leave on Saturday evening. Air New Zealand had no US departures from New Zealand due before then.

The US Federal Aviation Administration ordered a nationwide ground stop shortly before 10am Saturday New Zealand time, after first halting traffic in Chicago. US Transportation Secretary Sean Duffy said the communications failure affected the regional control centres that guide aircraft between airports and that FAA technicians were investigating.

Planes already in the air were allowed to land. The Associated Press reported that a small number of international flights later took off from airports on both US coasts after departures began being cleared individually. The initial order was due to run until at least 5pm Saturday New Zealand time. A time for normal departures to resume nationwide had yet to be confirmed.

The disruption was already visible at airports used by New Zealand travellers. In Los Angeles, an Alaska Airlines flight bound for Washington, DC, was taxiing towards the runway when it came to a halt. The San Francisco Chronicle reported that passengers crowded into a terminal at San Francisco International Airport to wait for updates. At Chicago O’Hare, some passengers who had already boarded were told to get off their planes.

Within about two hours of the nationwide order, aviation data company Cirium had recorded about 600 diversions, the Associated Press reported. Most of those flights returned to the airport they had left. Others landed at a different airport, leaving airlines to get aircraft and crews back into position as they worked through delays and cancellations.

US Homeland Security Secretary Markwayne Mullin said officials had seen no indication of a deliberate attack. The cause of the outage remained under investigation. It was the first nationwide ground stop since January 2023, when a failure in the FAA’s system for sending safety notices to pilots halted domestic departures for less than two hours.

Boyer said Air New Zealand would contact affected customers directly. Travellers can check the airline’s travel alerts page or the Air NZ app. Passengers connecting within the United States should also check their onward flight with the airline operating it.