There is a potential for flight delays in the US this Sunday due to a disruption in the Federal Aviation Administration’s significant NOTAM warning system. This issue arises shortly after the nation was shocked by two fatal plane accidents.

Secretary of Transportation Sean Duffy stated that the Notice to Air Missions system, which communicates crucial data about potential risks to pilots and airports, went offline on Saturday evening.

Despite the main NOTAM system experiencing a temporary outage, Secretary Duffy assured that the National Airspace System has not been affected as there is a backup system in place. The agency has activated alternate systems to ensure that flight operations continue without disruption.

Duffy added that the FAA was working to restore this system fully, but that “there may be some residual delays” going into Sunday morning.

According to data collected by FlightAware, there were nearly 500 delayed flights in the US, and a little over 60 cancellations early Sunday morning.

That information includes important communications such as runway closures, warnings about birds, or low-altitude construction obstacles.

The critical system is separate from air traffic control, which keeps planes a safe distance from each other.

Duffy did not say when officials expected the system to be up and running again.

The outage comes days after two horrifying plane crashes. The mid-air crash Wednesday between an Army Black Hawk helicopter and an American Airlines passenger plane landing at Ronald Reagan Washington National Airport killed 67 people — making it the deadliest US air disaster since 2001.

On Friday night, a medevac plane returning a sick girl to Mexico crashed after taking off from Northeast Philadelphia Airport — killing all six people aboard and one person on the ground.