How can I distinguish between a diverted flight and subsequent operation?

A Flight Status by Flight API call issued to our system we will return both flights, the original and subsequent operation if our system detects a status=Diverted from the data sources for the flight and there is a second attempt at departure on the same day. The original flight schedule published in advance by the carrier will be marked with a status=Diverted if detected from a source. If we are able to detect a subsequent operation or another attempt at departing from the originally scheduled airport, our system will treat this scenario by creating another Flight ID.

We recommend customers use the extendedOptions=includeNewFields query parameter to follow up with this subsequent flight. We suggest ignoring the flight with the status of "D" and use the other as long as the carrier and flight numbers match.
 
When requesting with flight status updates/deltas, you can use the relatedFlightId for any update that is of type SUBSEQUENT_OPERATION_BY to get the freshest details on the new record.