What we know about the longest US nationwide flight ground stoppage since 9/11

It was only the second such nationwide stoppage since the immediate aftermath of the al-Qaeda plane hijackings of 11 September 2001.

“This looks like the worst since 9/11, but clearly not on that scale,” Dr Guy Gratton, an associate professor of aviation at Cranfield University, told BBC Verify.

Dr Gratton pointed to a US grounding in 2023 due to a failure in the Notice to Air Missions (Notam) system.

“That lasted 1 hour and 52 minutes, delayed about 9,500 flights and cancelled about 1,300,” he said.

The 2023 outage meant air traffic safety notices could no longer be published, and flights were grounded until that system was restored.

But Friday’s incident lasted longer than the 2023 event.