WASHINGTON DC – Departures of domestic flights are resuming across the country after the Federal Aviation Administration restored a system that warns pilots of hazards during their upcoming flights.

The FAA first issued an advisory just past 4 a.m. on Wednesday that a technical issue impacted its Notice to Air Missions system (NOTAM), and it announced a couple hours later that it had ordered all airlines to pause domestic departures until 9 a.m. to ensure flight safety.

Thousands of flights were delayed and hundreds have been canceled, but airlines are gradually restoring normal operations.

Here’s five things to know about the system outage at the FAA:

The FAA is assessing the cause of the initial problem

The administration has not seen evidence of a cyberattack

Flights are back up and running

Travelers are likely to face delays throughout the day or longer

The outage prevented flights from taking off, not landing

Full details at The Hill