Flights across the U.S. are being affected by a computer outage. The FAA said on its website this morning that its “Notice to Air Missions” computer system had failed. The system contains information essential to workers involved in flight operations. A source with knowledge of the situation told NBC News that all flights in the U.S. were grounded following the incident. The FAA website said, “Operations across the National Airspace System are affected,” and added, “Technicians are currently working to restore the system and there is no estimate for restoration of service at this time.”