Updated

The Federal Aviation Administration grounded all flights at US airports on Friday, citing extraordinary circumstances and reasons of safety. The stop was caused by air traffic control communications problems, and passengers were stranded on tarmacs across the country. US officials said old equipment overloaded and the disruption was not a cyber-attack or a Microsoft outage. Homeland Security Secretary Markwayne Mullin said there were no indications of an attack, and the ground stop ended later Friday.