	Introduction

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. 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. It has allowed government agencies and operators of small commercial drones to obtain permits on a case-by-case basis. FAA's initiatives to regulate small unmanned aircraft systems pertain to those weighing less than 55 pounds. FAA has not proposed regulations relating to large UAS. The proliferation of these systems has complicated FAA's efforts to develop regulations allowing for the integration of UAS into the national airspace. More recently, FAA has backed away from projecting the potential size of the UAS market, noting only that once routine operations of small UAS are authorized, a surge in commercial uses of UAS is anticipated. The study estimated that the number of commercial UAS in the United States would grow to about 45,000 by 2029, at which point the number of commercial UAS is expected to surpass the number of UAS operated by the military, federal, and state and local government entities combined. That advisory outlines the requisite criteria to be considered a model aircraft operation as defined in Section 336 of FMRA and also
notes that model aircraft that endanger flight safety, particularly those that operate in a careless or reckless manner or interfere with or fail to give way to manned aircraft, may be subject to FAA enforcement action; warns that model aircraft operators must comply with any temporary flight restrictions imposed due to disasters, reasons of national security, or for the management of air traffic around air shows, major sporting events, or other events; states that model aircraft must not operate in prohibited airspace, special flight rules areas, or the flight-restricted zone around Washington, DC, without specific authorization; states that model aircraft operators must be familiar with Notices to Airmen (NOTAMs) addressing operations near military installations and federal facilities, certain stadiums, various critical infrastructure facilities, national parks, and emergency service operations; and advises that model aircraft operators should follow best practices including limiting operations to below 400 feet above ground level. Several UAS have been spotted over sporting events, and in some instances drones have crashed at public events such as football games and tennis matches. Enforcement

At present, UAS, and small UAS in particular, are largely segregated from manned aircraft operations as a safety measure. Effective December 21, 2015, all operators of model aircraft and hobby drones weighing between 250 grams and 55 pounds are required to register with FAA. Small UAS can be used by criminals and terrorists for espionage, surveillance, and intelligence gathering at critical government and industrial facilities. Chemical and biological agents pose a particular concern, as UAS used for aerial pesticide applications could readily serve as platforms to carry out attacks. UAS Detection and Countermeasures

The persisting security threats of UAS, along with safety concerns about unauthorized operations in restricted areas and near airports, has generated increasing interest in technology solutions to detect and, potentially, to disable unauthorized UAS activity. These include
developing capabilities to detect, sense, and avoid other air traffic, including both manned and other unmanned flights; mitigating risks to persons and property on the ground; preventing unauthorized use of airspace; providing adequate and adequately secure radiofrequency spectrum for command and control linkages and sensor payloads; and addressing human factors considerations including approaches to system automation, human-system interfaces, and operator training and qualification standards. A number of other bills addressing privacy and security concerns of domestic UAS operations have also been introduced. Safety, security, and privacy issues regarding domestic UAS operations and UAS integration are likely to be issues of particular interest in these deliberations.
Unmanned aircraft systems (UAS), often referred to as "drones," have become commonplace over the past few years. As UAS technology develops rapidly, the United States faces significant challenges in balancing safety requirements, privacy concerns, and economic interests.
The FAA Modernization and Reform Act of 2012 (FMRA; P.L. 112-95) required the Federal Aviation Administration (FAA) to develop and implement a comprehensive plan to integrate unmanned aircraft into the national airspace and issue regulations governing the operation of small unmanned aircraft used for commercial purposes. FAA has proposed regulations allowing routine operations of small commercial UAS weighing less than 55 pounds, but is still developing the guidelines and standards for federal, state, and local government agencies required by FMRA. Hundreds of thousands of small UAS are already being operated as recreational model aircraft and hobby drones that are permitted under a special rule for model aircraft established by FMRA. In addition, several hundred public agencies and more than 3,000 businesses have been granted approval to operate UAS on a case-by-case basis. Once regulations and guidelines are put in place, large growth in UAS operations is anticipated.
As UAS operations have increased, a number of safety concerns have emerged, particularly with regard to use of model aircraft and hobby drones. UAS flights have interfered with airline crews near busy airports and with aircraft fighting wildfires, and have posed safety and security hazards at outdoor events and in restricted areas. FAA has been addressing these concerns through user education initiatives and in limited cases by using its enforcement authority to sanction unauthorized and unsafe operations. In an effort to better monitor UAS operations and carry out enforcement actions as appropriate, FAA now requires that commercial and recreational UAS operators register all small UAS weighing between 250 grams and 55 pounds. Technology known as "geo-fencing" may play a future role in keeping UAS away from airports and other restricted airspace by overriding operator inputs and keeping UAS out of these areas.
UAS could potentially be used by criminals and terrorists for espionage and smuggling, or as a platform to launch a remote attack. To address both safety and security concerns, a number of technology solutions are being examined to detect airborne UAS and pinpoint the location of the operator. Technologies to disable, jam, take control over, or potentially destroy a small UAS are also being developed and tested.
Many of the commercial applications envisioned for UAS, such as express package delivery, remote monitoring of utilities and infrastructure, and imagery collection and analysis to support precision agriculture, most likely will not be viable without development of technological capabilities that allow for the complete integration of UAS in the national airspace. These include technologies to enable drones to sense and avoid other air traffic; manage low-altitude airspace and detect and prevent unauthorized use of airspace; mitigate risks to persons and property on the ground; provide secure command and control linkages between drone aircraft and their operators; and enable automated operations. There are also issues related to operator training and operator qualification standards. A number of bills introduced in the 114th Congress address UAS safety, and these topics may be considered in further detail in forthcoming FAA reauthorization debate.