American Airlines was hit by a massive IT outage on Tuesday afternoon prompting the FAA to issue a ground stop for all non-air-borne American flights.

It started with reports of users on social media and on Down Detector, a platform that tracks such outages based on users’ reports. Users complained that the American Airlines user-end system was not working, which included the carrier’s app and website. As many as 15000 people reported issues with the American Airlines platform on Down Detector.

Shortly afterwards, the Federal Aviation Administration issued a ground stop for all American Airlines aircraft that are not currently airborne, impacting American travelers in the United States and across the world.

This story is being updated.