This special issue on Unmanned Aerial Systems (UAS) for Environmental Applications makes three important contributions: (1) It marks the launch of a new section in the International Journal of Remote Sensing (IJRS), which we have called Drones. (2) It captures key contributions from the 5 th Small Unmanned Aerial Systems (sUAS) for Environmental Research (UAS4Enviro2017) conference, which was held at the University of Trás-os-Montes e Alto Douro, Portugal, from 28 to 30 of June 2017. (3) It collects a wide range of papers on UAS, in addition to those presented at the conference. Drones are indeed a key new technology for remote sensing, and one that has grown rapidly in recent years. According to the database, Web of Science (published by Clarivate Analytics), the first significant use in IJRS of any of the terms UAS, unmanned aerial vehicle (UAV) or drones, for example, in the title, abstract, or keyword of an article, was in 2009, in a paper by Dunford et al. (2009). It was not until 2012 that another paper used one of those terms. After that, the numbers increased very quickly, and by 2017, IJRS published 68 papers that referenced these terms. Most notably, 2017 also saw the first IJRS special issue on UAS, titled 'Unmanned aerial vehicles for environmental applications' (The Editors 2017). This current special issue is a direct follow-on from that major collection of papers, and the fact that we are able to have two major special issues on this topic in the space of just over one year, is further evidence of its importance. By placing UAS papers in the new Drones section of IJRS, we aim to foster dialogue amongst the UAS community, and highlight the rapid advances made in this field. However, the need for a separate section for drone-related work may not seem CONTACT Anita Simic Milas