Photogrammetric studies performed with Unmanned Aerial Vehicles (UAV) have recently become more popular as they present an interesting low-cost alternative. A novel application of thermography with UAVs has been validated during the last years: aerial thermography for inspection of photovoltaic plants as a useful diagnostic technique to assess performance of photovoltaic modules, superseding time-consuming traditional manual methods. This paper describes the current state of thermographic cameras and UAV technology, with the aim of examining the general principles of aerial thermographic measurement and required instrumentation, detailing the most important system aspects, discussing new developments and future trends in aerial thermography sensors and instrumentation, and evaluating them for specific application of aerial thermographic inspection of photovoltaic plants.