An upgrade to a decades-old telecoms network in the US led to the longest nationwide grounding of flights since the 11 September 2001 attacks. The stoppage on Friday occurred when a key system for air traffic controllers and pilots to communicate was switched from old copper wiring to fibre.
US Transportation Secretary Sean Duffy stated on Saturday that a government contractor, L3Harris, was upgrading the aviation telecoms network. During this process, a router installed by L3Harris began flooding other routers in the air traffic control system, sending 1,000 connection attempts every four to five seconds.
This resulted in "instability" on voice and ground communications at 17 out of 22 air route traffic control centres in the US, according to Bryan Bedford, administrator of the Federal Aviation Administration (FAA). The FAA took 45 minutes to identify the problem due to maintenance being logged manually on paper. As a precaution, all flights were grounded.
The ground stop led to over 8,500 delayed and nearly 8,000 cancelled flights on Friday. While US authorities stated that full operations had resumed on Saturday, more than 5,900 flights were cancelled and over 7,000 delayed in the US on Saturday as the system unwound the disruption.