In February 2012, President Obama signed the FAA Modernization and Reform Act of 2012 (FMRA; P.L. 112-95 ). The legislation mandated that the Federal Aviation Administration (FAA) develop a comprehensive plan to integrate unmanned aircraft systems (UAS) into the national airspace and begin implementing the plan starting in October 2015. FRMA also required FAA to issue regulations pertainin g to small commercial drones and develop standards for the operation and certification of unmanned aircraft operated by federal, state, or local government. Deadlines for completing these actions have passed, but FAA has not yet finalized its UAS regulations and standards. However, FAA is granting approvals to government agencies and commercial operators to operate certain UAS on a case-by-case basis. Under a special rule established by FMRA, model aircraft and hobby drones operated strictly for noncommercial recreational purposes are permitted to fly below 400 feet so long as they remain within sight of the operator, outside of restricted airspace, and away from airports unless appropriate prior notification has been given to airport operators and air traffic control towers. Under this rule, operations of hobby drones have proliferated, creating significant enforcement challenges for FAA. Meanwhile, FAA has proceeded slowly and cautiously in complying with the FMRA mandate related to government and commercial operations. It has allowed government agencies and operators of small commercial drones to obtain permits on a case-by-case basis. In February 2015, FAA proposed regulations allowing for the routine operation of small commercial UAS; these rules are expected to be finalized in April 2016. FAA's integration plan, developed in response to FRMA requirements, indicates that procedures allowing public safety UAS routine access to airspace are forthcoming. FAA's approach to regulation distinguishes between operations conducted within visual line of sight (VLOS) and those involving flight beyond (visual) line of sight (BLOS). This distinction does not depend on aircraft size. Some small UAS can achieve basic BLOS capability using a live feed from an onboard camera presented to the operator on a visual display. Larger UAS operated from dedicated control stations achieve BLOS capability through similar means, but also often include other sensing capabilities such as moving map displays, airborne radar information, and air traffic collision avoidance systems to enhance operator situational awareness. So far, FAA is restricting commercial users and model aircraft operators to VLOS operations. The proposed rule for commercial UAS would maintain this restriction, a limitation that would rule out many potential uses of UAS, such as aerial surveying and inspections and package delivery. Furthermore, FAA requires that each UAS be controlled by a dedicated pilot operating one aircraft at a time, just as occurs with manned aircraft. It has proposed formal training requirements for commercial UAS operators similar to the certification process for pilots of manned aircraft. However, UAS technology is rapidly pushing in the direction of greater autonomy and automation. Operational concepts for potential BLOS applications envision systems that will involve minimal human input and interaction and minimal training to operate. Many of the anticipated uses envisioned for UAS, particularly those involving BLOS operations, will require that unmanned aircraft be integrated with manned aircraft within the national airspace system. At the current level of maturity, however, most UAS are being kept segregated from manned aircraft and controlled airspace through altitude restrictions and the establishment of strict airspace boundaries. In the future, it is anticipated that some UAS will share airspace, and potentially share facilities like airports and helipads, with manned aircraft. Technological innovations, as well as standardized procedures operators must follow, will be needed for full integration. An unmanned aircraft is a vehicle designed for flight that does not have a human operator, a pilot, on board. Most unmanned aircraft are controlled from a ground station. The aircraft, its ground station, and command and control radio linkages between the two are collectively known as an unmanned aircraft system. For small UAS, the ground station may be nothing more than a handheld radio control device with manual inputs. More sophisticated drones have ground control centers that look similar to cockpits of modern airliners. Unmanned aircraft are generally classified based on their size and weight. FAA's initiatives to regulate small unmanned aircraft systems pertain to those weighing less than 55 pounds. FAA has also suggested a possible sub-category called micro-UAS, which would be limited to 4.4 pounds (2 kilograms) and thus might pose fewer safety concerns. Unmanned aircraft 55 pounds and greater are categorized as large insofar as they do not meet the statutory or regulatory requirements to be considered small UAS. FAA has not proposed regulations relating to large UAS. An unmanned aircraft's size and weight are generally correlated with both its operating altitude and its flight endurance. Small UAS operate at the lowest altitudes (typically below 1,000 feet) and have comparatively short endurance, usually 30 minutes or less. Many of the consumer drone products that fall into this category are battery-powered, and include rotary-wing designs, such as multi-copter drones, as well as more traditional fixed-wing airplane designs. Some larger designs are gasoline-powered and can operate up to several thousand feet. More capable gasoline-powered unmanned aircraft originally designed as military systems, like the fixed-wing ScanEagle and Fire Scout helicopter, and larger UAS like the Predator/Guardian and the jet-powered Global Hawk, can be deployed for several hours, have thousands of miles of effective range, and operate at medium and high altitudes (see Figure 1 ). The history of unmanned aircraft goes back about a century, to the latter years of World War I, when prototype fixed-wing unmanned aircraft were developed. This research was important in the development of guided missiles and target drones during World War II and the Cold War era. In the 1980s, spurred by Israeli initiatives, the military developed more sophisticated unmanned systems with extensive ground-based command-and-control capabilities and more advanced onboard imaging sensors. Unmanned aircraft were used by U.S. forces for intelligence missions in Kosovo in the late 1990s, and in Afghanistan and Iraq for reconnaissance and surveillance as well as, more recently, for combat missions. Interest in nonmilitary uses of UAS increased following the 9/11 terrorist attacks in 2001. In FY2004, Customs and Border Protection (CBP) began testing unmanned border surveillance missions, and in FY2005, CBP began operational use of UAS along the southern border. Such uses are allowed under certificates of authorization (COAs) issued on a case-by-case basis by FAA. The Federal Bureau of Investigation (FBI) has deployed small unmanned aircraft on a limited basis to provide targeted aerial surveillance for search and rescue operations, kidnapping investigations, fugitive manhunts, anti-drug trafficking interdictions, and national security missions. However, UAS have so far played a limited role in law enforcement. While there are about 18,000 police agencies in the United States, fewer than 50 have obtained FAA authorization for unmanned flight operations. Many federal, state, and local agencies involved in law enforcement and homeland security appear to be awaiting more specific guidance from FAA regarding the routine operation of public-use unmanned aircraft. Legal issues related to individuals' privacy interests protected under the Fourth Amendment have also slowed the adoption of drones for domestic surveillance and homeland security operations. Use of UAS by fire departments has been even more limited, even though there are about 30,000 fire departments in the United States. To date, fire services have mainly used UAS for wildfire and search and rescue operations in remote areas. Applications in urban and suburban environments are being evaluated by several fire departments. The Fire Department of New York City envisions that a tethered UAS it is currently testing would be deployed at second alarm and greater fires and other emergency incidents to provide aerial surveillance to assess dangers to firefighters and other responders. Section 334 of FMRA directed FAA to address routine access to the national airspace by public safety agencies, and develop standards for operation and certification by such agencies by the end of 2015. However, this deadline has now passed, and it remains unclear what actions FAA may take to meet this mandate. Federal government use of UAS includes other applications such as land management, wildfire monitoring, earth imaging and weather monitoring, and scientific research. Among federal agencies, research use by the National Aeronautics and Space Administration (NASA) currently accounts for almost half of the active UAS authorizations. Department of Homeland Security activities, predominantly CBP surveillance missions along U.S. borders and over territorial waters, comprised about 16% of active UAS authorizations as of January 2015. Other agencies using UAS include the National Oceanic and Atmospheric Administration (NOAA) and the Department of the Interior. A small number of state agencies have obtained approvals to operate UAS for aerial surveying and to monitor the environment, highways, and other infrastructure. State university research programs currently are the largest nonfederal government use of UAS. Many of the near-term applications of unmanned aircraft for both government and business involve data collection using a broad array of devices. Digital cameras are the most common data collection sensors aboard UAS. Additionally, UAS may be equipped with infrared sensors that provide night vision capability, more specialized imaging sensors such as synthetic aperture radar, light detection and ranging (LIDAR) systems that use laser scans to capture high-resolution contour maps and images, or multispectral imaging systems that capture a broad spectral range both within and beyond the limits of human vision. Recreational model aviation using radio-controlled airplanes emerged as an organized hobby activity in the 1930s as enthusiasts sought to emulate some of the feats of the great air races of the time. It has remained a popular pastime ever since.