The FAA grounded all departing flights across the US today, only the second such nationwide stop since 9/11, and it's bad news for travelers heading into the holiday season.

• The FAA cited "safety reasons" and a communications breakdown hitting air traffic control centers, with early reports pointing to a cascading radio frequency outage.
• Thousands of planes already in the air were allowed to keep flying, but no new departures were allowed to take off, leading to thousands of delays and hundreds of cancellations within hours.
• International arrivals are being handled case by case, and the ground stop was expected to last several hours.
• The outage raises questions about aging air traffic control technology (some systems reportedly still run on decades-old equipment) just as the FAA was rolling out a new AI-assisted traffic management system called SMART.
• Separately, a tanker collided with a cruise ship near the Port of New Orleans, adding to a string of recent transportation mishaps including a cargo plane crash in Miami and a Microsoft cloud outage.

Outlook: Expect flight delays and cancellations to keep piling up through the day, with the timing raising concerns about travel disruptions heading into the Thanksgiving and holiday rush.