Ranking Democrat Member of the House Committee on Transportation and Infrastructure Rick Larsen of Washington state issued the following statement regarding the FAA-ordered ground stop today:

"This morning, the Federal Aviation Administration issued an order pausing all domestic flight traffic due to a disruption to their Notice to Air Missions system," Ranking Member Larsen said. "I spoke with Secretary Buttigieg about this development and will continue to monitor this disruption to our air travel system until it is resolved."

Delta Air Lines says it remains connected with the FAA as it works to mitigate the impact of the ground stop the agency implemented earlier today.

“A fare difference waiver will give customers additional flexibility even if their flight isn’t delayed or cancelled,” the airline says.

One of the immediate concerns for airlines will be congestion within airports making getting things back on track more difficult. The move by Delta allows passengers to switch flights and avoid airports completely today even if their flight is not affected.

Secretary of Transportation Pete Buttigieg has rejected the suggestion that the Federal Aviation Administration should reimburse affected travellers who have had flights cancelled or delayed by the decision to order a ground stop.

He told MSNBC: “We’re not a for-profit company selling tickets ... We’re always going to err on the side of safety.”

In a statement regarding the resumption of operations, American Airlines says that more than 950 mainline and regional flights have departed, but some 450 have been cancelled and another 850 have been delayed.

American has resumed operations now that the Federal Aviation Administration's nationwide ground stop has ended. We continue to closely monitor the situation, which impacts all airlines, and are working to minimize further disruption to our customers and operation. To support our customers whose travel was affected by the FAA system issue, we're providing additional flexibility to rebook their travel plans today and tomorrow without any additional fees.

Senate Majority Leader Chuck Schumer says he has spoken to Secretary Buttigieg about the restoration of air travel.

He adds: “While at this moment there’s no clear evidence of outside interference, the FAA needs to get to root causes so this doesn’t happen again.”

Joe Sommerlad explains how today’s air travel turmoil came about.

NAV Canada, the country’s air navigation service provider, has tweeted out a message stating that its own NOTAM system is experiencing an outage affecting newly issued notices.

So far no delays are reported relating to the outage.

Major airlines, from most impacted to least: Southwest (48 per cent of flights delayed), American Airlines (44 per cent), Spirit (40 per cent), Delta (37 per cent), United (36 per cent), and JetBlue (31 per cent). West coast-focussed airlines such as Alaskan and Hawaiian show a modest number of delays as the outage occurred at a time when they have a lower number of scheduled flights.

The worst affected airports for delays are Baltimore (49 per cent of flights delayed); LaGuardia (44 per cent); Atlanta, Chicago Midway and Orlando (39 per cent); Denver and Nashville 37 per cent; and Reagan National, Austin, and Tampa (36 per cent).

Almost every major airport now has more than 25 per cent of its flights delayed.

If you are travelling today, check the status of your flight with your airline, as airports will be busier than usual.