Batteries are less energy dense (J/kg) than fossil fuels at any scale. For flight applications this makes batteries not so great because reducing weight is so c

Batteries are less energy dense (J/kg) than fossil fuels at any scale. For flight applications this makes batteries not so great because reducing weight is so critical. This becomes especially pronounced for larger aircraft sizes. You also don't get the weight reduction as you burn off fuel. For tiny RC aircraft the short flight times are fine, you can use cheap electric motors and they're safer. Larger RC aircraft are gas powered though.