The United States lifts its flight suspension order. More than 4,700 flights across the United States are canceled and 10,000 flights are delayed.

The U.S. Federal Aviation Administration (FAA) lifted the nationwide flight suspension order today. Previously, a communication failure occurred at the air traffic control center, causing chaos at airports across the country and triggering the longest nationwide flight suspension since the 9/11 terrorist attacks in 2001.

According to reports from AFP and Reuters, according to the flight tracking website FlightRadar24, more than 4,700 flights were canceled and 10,000 flights were delayed on the 13th. About 700 flights on the 14th were also cancelled. Aviation industry analysts said it may take airlines several days to resume normal schedules after flights across the United States were suspended for more than four hours.

U.S. Transportation Secretary Sean Duffy said flights across the United States can resume and blamed the air traffic chaos on old hardware.

The U.S. Department of Homeland Security said there is currently no indication that the communications system outage was caused by a cyber attack.

The failure is the latest and most serious symptom of long-term stress on the U.S. air traffic control system. The system has long faced equipment and communications problems, controller manpower shortages, and aging infrastructure.