U.S. aviation authorities temporarily grounded all flights across the country Wednesday morning due to a system glitch, causing a massive disruption in airline departures. The Federal Aviation Administration said the problem affected the Notice to Air Missions, a system providing airplanes and airports with safety information including on natural disasters. The White House denied the system had come under cyberattack. The FAA issued an order for all airlines to suspend departures, but lifted it before 9 a.m. Eastern time. The Associated Press said the decision caused delays for more than 2,500…