The November 13, 2026, FAA nationwide ground stop stemmed from a sudden telecommunications outage that disrupted radio frequencies, radar, and automation across multiple Air Route Traffic Control Centers, halting departures while allowing inbound flights to land. Official statements from the FAA and Transportation Secretary described a temporary communications failure, with technicians actively investigating the root cause. Reports indicate an update to the private ATC communications network may have triggered a system reboot and crash, though this remains unconfirmed and distinct from any Microsoft outage the prior day. Homeland Security officials ruled out early signs of a cyberattack. This marks only the second such stop since 2023’s NOTAM software glitch. Traders should watch for the FAA’s formal post-incident report, which will likely clarify whether the failure traces to a software update, database synchronization error, or infrastructure vulnerability.