The United States stopped every departing flight in the country for more than four hours on Friday after a telecommunications failure cut communications at air traffic control centres, in one of the broadest shutdowns of American airspace in years.

The Federal Aviation Administration issued the nationwide ground stop at 3.54pm Eastern Time — 2054 GMT, or about 2.24am Saturday in Colombo — and reopened the airspace at 8.15pm Eastern (0115 GMT), Al Jazeera reported.

The agency described the cause as a “temporary telecommunications outage” and said it had halted departures out of an abundance of caution. The problem affected all 22 air route traffic control centres, the facilities that guide aircraft between airports.

The scale

More than 10,000 flights were delayed and more than 4,000 cancelled, according to the tracking service FlightAware as cited by CBS News in Al Jazeera’s report.

Hiru News, citing foreign reports, put the number of aircraft already en route to US airports at about 4,042 when the order was issued, and said decisions on international arrivals were being taken case by case.

When the stop was lifted, CNN’s coverage was headlined “FAA says airlines can resume flights after hours-long ground stop, but delays and cancellations to continue” — the disruption is expected to run past the shutdown itself.

Not an attack, officials said

Markwayne Mullin, the Homeland Security Secretary, told reporters there was no indication the ground stop had been triggered by a threat.

“Everybody’s safe. The flights are accounted for. This is not another 9/11.”

The FBI does not believe a cyberattack or criminal activity caused the failure, Bloomberg reported citing an official familiar with the matter. Transportation Secretary Sean Duffy described the problem as a communication issue.

Investigators were examining whether a software update caused the outage, though no cause had been established at the time of the reporting.

Not reported

No filing gives a confirmed root cause, says how long full schedule recovery will take, or identifies which carriers were worst affected. None of the sources reports any effect on Sri Lankan travellers or on routes serving Colombo, and this desk has not independently established whether there was one.

Hiru’s filing, published at 6.28am Colombo time on Saturday, was written while the stop was still in force and carries no reopening time; the reopening is taken here from Al Jazeera and CNN, which filed after the airspace was cleared.