Local Data Mode is a DJI setting that disconnects the flight app from the internet. In practice, it is a privacy and exposure-reduction control: the app can operate without sending data to cloud services, which helps limit telemetry, account traffic, and some remote attack paths. For drone operators, that matters because the mobile app is part of the trust chain, not just a convenience layer.
Security-wise, Local Data Mode can reduce the damage from cloud account compromise, malicious third-party services, or network monitoring of app traffic. It is not a full offline guarantee, however. The aircraft, controller, firmware, and update workflow may still have separate connectivity requirements, and a compromised device or malicious local app still remains a risk. Defenders use this mode to minimize data exposure, but they should also verify update sources, manage device permissions, and treat the drone platform as a connected system rather than an isolated machine.