On January 11, flights across the United States were grounded after the Federal Aviation Administration suffered an outage. Reportedly, a technical glitch led to the disruption. Later, the US Federal Aviation Administration (FAA) tweeted saying that normal air traffic operations are resuming gradually across the country. Earlier, the FAA had tweeted informing that they are working to restore its Notice to Air Missions System (NOTAM). US President Joe Biden ordered an investigation and said that the cause was not known, reported Reuters. Watch the video to know more.