In this letter, we develop channel models for unmanned aerial vehicle-aided air-to-ground (AtG) radio frequency energy transfer (RFET). AtG path loss plays a key role in RFET-based recharging of field nodes. Representative field environments consist of different types of built-up areas, namely, suburban, urban, dense urban, urban high-rise, and rural agriculture deployment scenarios. For emulating the built-up areas, ITU-R recommendations are considered, whereas for rural agricultural field deployment scenario, dynamics of vegetation growth with time is considered. Accuracy of the proposed path loss models are validated by conducting real AtG radio frequency transmission experiments in emulated suburban and agricultural fields.