Definition
A radio call from ATC informing a pilot that previously issued traffic — another aircraft that was called out as a potential conflict — is no longer a concern. The other aircraft has either passed, turned away, descended, climbed, or otherwise moved out of conflict, so the pilot no longer needs to watch for it or take action to avoid it.
Plain English
The controller is telling you the other airplane they warned you about is no longer something you need to worry about.
Context Anchor
You may hear this on the radio after air traffic control has already called out nearby traffic and then determines that the aircraft is no longer a concern.
Why Pilots Care
Confirms the pilot may discontinue the visual search for that traffic and return full attention to primary flight tasks and other traffic.
Intuition Check
Do not read “no longer a factor” as “there is no other traffic anywhere.” It only means the specific traffic that was previously pointed out is no longer a concern for your flight at that moment.
Example Sentence 1
After the Cessna passed behind us, the controller said, "Skyhawk Three Four Tango, that traffic is no longer a factor."
Example Sentence 2
After receiving advisories that traffic is no longer a factor, the pilot resumed normal instrument scan during the arrival.