What forced the US to ground all planes? A router switch, we now know

A routine router replacement in the US air traffic control network triggered a nationwide flight ground stop on Friday, after equipment overload caused communication and radar gaps. Officials say the disruption was not a cyberattack, but it led to thousands of cancellations and delays and renewed concerns about the reliability of ageing aviation systems.

The FAA stopped flights at 3:54pm East Coast time and lifted the restriction more than four hours later, at 8:15pm. More than 9,000 US flights were cancelled on Friday and over 5,000 on Saturday as backlogs continued. The work involved replacing copper wire with fibre-optic lines; the Transportation Secretary said a faulty device or contractor error caused one router to flood others with about 1,000 connection attempts every four to five seconds, affecting 17 of 22 FAA en route centres.