An unmanned aerial vehicle (“UAV”) is configured with a redundant power generation system on-board the UAV. A redundant power system on-board the UAV can selectively utilize an auxiliary power source during operation and/or flight of the UAV. The power system on-board the UAV may include a battery and at least one auxiliary power source comprising a combustion engine. The combustion engine on-board the UAV may be selectively operated to charge the battery when a charge level of the battery is below a full charge level, and/or to power one or more propeller motors of the UAV.