Officials from more than one agency involved in the inquiry have now told NBC News there is no indication the FAA communications outage was caused by malicious activity. That widens the sourcing on a line first reported by CNN, which cited two law enforcement officials.
NBC News reports that the officials said they had not seen evidence of the type of activity normally linked to a cyber attack.
Three senior officials also told NBC News that nothing connects the FAA incident to Microsoft's widespread outage.
The officials cautioned that it is early in the investigation and that findings can change as it goes on.
None of the officials is named, and the report has not been independently checked.