Sean Duffy Offers New Details on How One Fix Spiraled Into Nationwide Ground Stop

The cascade of failures that led to the grounding of U.S.air traffic on Friday began with what officials say was supposed to be a routine router upgrade at a radio facility in El Dorado, Ark.

The station was remote enough, they figured, that they could do the work without causing undue harm.But that swiftly proved to be a gross miscalculation.The effort to upgrade the Federal Aviation Administration’s antiquated copper-wire-based system to fiber optic cable in Arkansas occurred as the agency officials noticed a second issue with a radar facility in Amarillo, Texas, where such work had been done weeks before, Transportation Secretary Sean Duffy said Sunday morning during a blitz of appearances across network and cable television.Officials took the two facilities offline shortly after, but not before each had pinged the network with an abnormally high rate of connections.That prompted failures in other parts of the air traffic communications network that forced officials to declare a rare nationwide ground stop, Rebecca Guy, the F.A.A.’s chief technology officer, told reporters on Saturday.But agency investigators still have not determined whether a faulty part or an error on the part of L3Harris, which owns the telecoms system in question and is responsible for upgrading and maintaining it, caused the initial problem in Arkansas.

And Mr.Duffy said they are equally unsure why the facility in Amarillo failed on Friday when no upgrade work was being done there at the time.The protracted crisis, from which airlines have yet to recover, and the lack of clarity from Trump administration officials about why things went wrong, have revived questions about whether the F.A.A.

is equipped to carry out its plan for modernization without creating more risks for the nation’s air traffic control system.The crisis has also heightened concerns about durability and the lack of backups in the nation’s critical air traffic infrastructure, if a failure at one small facility is...