WASHINGTON (AP) — The Federal Aviation Administration said Tuesday it is forming a panel to examine the reliability of a telecommunications network that broke down last month, snarling air traffic across the country.

The Nov. 19 episode — which resulted in delays of 819 flights and forced air traffic controllers to manually enter flight information into computers — was unacceptable, FAA Administrator Randy Babbitt said in a statement. He said the agency needs to understand what happened so that it can prevent further incidents.

FAA said at the time that the incident began with the failure of a single circuit board in a router. A backup circuit board also failed. As a result, misinformation was sent to FAA computer centers near Atlanta and Salt Lake City. It was four hours before the glitch was fixed.