The union representing FAA technicians says its members played no part in the upgrade work that preceded the nationwide US ground stop.
"PASS-represented technicians were not involved in the upgrades that led to the ground stop yesterday,"
That is from the Professional Aviation Safety Specialists (PASS) union, in a statement quoted by Yahoo News. PASS represents more than 11,000 FAA employees.
The statement came after Transportation Secretary Sean Duffy named the contractor L3Harris as the company updating communications infrastructure at the time. Duffy has said the fault began during a switch from copper to fibre lines at a remote FAA site, "either through contractor error or a faulty piece of equipment". L3Harris has said it is supporting the FAA's investigation but has not addressed his suggestion of contractor error.
PASS also says contractors have historically followed a protocol in which FAA employees conduct a risk assessment and coordinate maintenance of the system or equipment. The union did not say whether that protocol was followed in this case.
The union's account is consistent with Duffy's statement that a contractor was carrying out the work. It has not been independently checked.