In recent decades, research into energy production and battery technologies in the space, military and civil industries have taken huge strides. These advances have sparked new ideas and innovations in defence industries and militaries around the world. This article focuses on how technological advances in solar and battery power create opportunities for the research and development of unmanned aerial vehicles (UAVs). It draws on how some technologies help militaries overcome strategic and political obstacles. It focuses on the development of the Zephyr solar UAV, as representative of the technologies that magnify the positive and negative implications of UAV use for military and commercial purposes. The article concludes that as solar and battery technologies get cheaper, this may lead to increased proliferation of UAVs, since the operational cost of solar UAVs is less than their fueldriven counterparts and offer unique and superior capabilities. While battery energy density has a long way to go match fossil fuel power, if energy density can double, then it would be possible to see electric jetsized planes in the 2020s. However, solar UAV development may magnify the security, political and judicial dilemmas that already exist with UAV use.