Why US grounded every plane for only 2nd time since 9/11; what happens next…

Air travel across the United States was thrown into disruption after the Federal Aviation Administration (FAA) ordered a rare nationwide ground stop, halting departures from airports across the country for more than four hours. Around 1.5 million passengers were affected as radar and communication systems reportedly became unstable at air traffic control centres. The incident also raised questions about the condition of America's ageing air traffic control infrastructure and whether a recently expanded AI tool played any role. Flights resumed later that evening, but delays continued to affect travellers. So, what caused the shutdown, and what does it reveal about US aviation safety?