Airborne longwave-infrared (LWIR) spectral imaging is shown to be effective for the high-confidence detection and identification (ID) of photovoltaic (PV) solar panels in both wilderness and urban settings. A series of baseline fiducial measurements were acquired during a controlled experiment conducted against a test array consisting of seven PV solar panels of areas ranging from <0.5 to almost 40 m2 assembled in a desert environment so as to minimize spectral clutter. The detection protocol deriving from this experiment was then successfully validated through an aerial survey of PV solar installations carried out in a spectrally and structurally complex urban environment. LWIR detection of PV solar panels offers a capability complementary with existing visible-shortwave infrared (VSWIR) methodologies.