The FAA issued a nationwide ground stop on Friday, halting all U.S. departures due to a radio communications outage. The agency cited extraordinary circumstances and reasons of safety for the order. Technicians are investigating the issue, while flights already in the air continue to land at their scheduled destinations safely.

All US departures have been delayed amid an air traffic control communications outage. Here's what we know so far:

An extremely rare nationwide ground stop is bringing air travel across the U.S. to a halt after an apparent radio communications outage disrupted air traffic control operations.

The Federal Aviation Administration (FAA) issued the sweeping order Friday, directing all U.S. airports to stop departing flights until further notice. The agency cited "extraordinary circumstances" and "reasons of safety" in an air traffic control advisory.

Reports indicate problems began around 3:30 p.m. ET at the FAA's Kansas City Air Traffic Control Center before spreading to other centers.

Flight-tracking service Flightradar24 and Canadian air traffic control have linked the disruption to an FAA radio outage.

Officials say FAA technicians are actively investigating the issue.

Approximately 3,100 aircraft are currently airborne and bound for U.S. airports, while no additional aircraft are taking off under the nationwide order.

Flights already in the air will be allowed to land. However, inbound international flights will be handled on a case-by-case basis, according to the FAA.

The last nationwide ground stops of this scale occurred on Sept. 11, 2001, and in January 2023, when an FAA system used to distribute critical flight safety notices, known as NOTAM (Notice to Air Missions), failed.

The cause of Friday's outage has not yet been determined, and it is unclear how long the ground stop will remain in effect.

While the ground stop itself does not appear to be weather-related, Mother Nature could complicate efforts to rebook flights over the weekend.

The West coast is set to get rounds of rain this weekend, while parts of the Northeast are still cleaning up after a nor'easter. Travelers who manage to secure new flights could find themselves running into additional weather-related delays.

If you are scheduled to fly Friday or over the weekend, check directly with your airline for the latest flight information before heading to the airport.