Although US authorities have found no evidence of a deliberate cyberattack, several of the country's leading security and intelligence agencies have launched a wide-ranging investigation into the incident that paralysed parts of the national aviation system, disrupted thousands of flights and stranded an estimated 1.5 million passengers.

The disruption, which occurred on 13 November, forced the US Federal Aviation Administration (FAA) to issue a rare nationwide suspension of flight departures after a serious telecommunications and communications systems failure affected air traffic control operations across the country.

Given the scale of the disruption and its potential implications for national security, the Federal Bureau of Investigation (FBI), the Department of Homeland Security and the National Security Agency (NSA) rapidly initiated coordinated inquiries to determine whether hostile actors could have been involved.

Investigators have focused on examining how critical aviation systems connect with external networks, reviewing whether any vulnerabilities within those links could have been exploited. Officials are particularly scrutinising ageing infrastructure, legacy communications systems and the resilience of aviation networks against increasingly sophisticated cyber threats.

However, senior US security officials indicated that, by the end of 13 November, investigators had not identified any signs suggesting the outage was the result of a targeted attack or sabotage operation.

Authorities are increasingly assessing whether a communications software fault or technical malfunction was responsible for the disruption. Even so, cybersecurity specialists and federal investigators continue to conduct an exhaustive review, noting that sophisticated cyber intrusions can sometimes remain hidden within complex systems for extended periods before being detected.

Security officials have also acknowledged that the US aviation network relies on infrastructure spread across numerous locations and, in some cases, incorporates older technologies, making inspections and security assessments particularly challenging.

Speaking during a White House briefing, Homeland Security Secretary Markwayne Mullin stressed that investigators had found no evidence of a cyberattack and sought to reassure the travelling public about safety throughout the incident.

"The public was never in danger throughout this process. No lives were threatened. No flights were at risk," Mullin said.

He also rejected suggestions that the aviation disruption was linked to a separate Microsoft service outage reported the previous day, emphasising that the FAA's decision to halt departures nationwide had been taken purely as a precautionary safety measure.

The FAA subsequently lifted the nationwide ground stop after more than four hours, allowing flight operations to resume gradually. Nevertheless, the impact on the aviation sector remained substantial, with airlines and airports facing significant operational challenges well into the following day.

According to aviation analytics firm Cirium, approximately 1.5 million passengers were affected by cancellations and extensive delays. Thousands of flights experienced knock-on disruptions as airport systems struggled to recover from the unprecedented interruption.

Congestion became particularly severe at some major hubs. At Ronald Reagan Washington National Airport, aircraft parking capacity was exhausted, forcing the airport temporarily to stop accepting diverted flights.

The consequences were also felt internationally. At the FAA's request, Eurocontrol suspended departures from 42 member states to destinations in the United States, while numerous flights from key Asian aviation hubs, including Seoul, Hong Kong, Shanghai and Singapore, were delayed or cancelled.

The disruption comes at a time when the United States is pursuing a multibillion-dollar effort to modernise its air traffic control infrastructure, an initiative intended to improve reliability, efficiency and resilience across one of the world's busiest aviation networks.

Although flight schedules have gradually returned to normal, federal authorities continue to scrutinise the entire aviation communications architecture. The ongoing investigation reflects continuing concern that critical transportation infrastructure must remain protected against both technical failures and evolving cybersecurity risks, even when no evidence of malicious activity has been identified.

Agencies