Unmanned aerial vehicles are used across the world for civilian, commercial, as well as military applications. In fact, "Drone Industry Insights" (a commercial drone market consultancy in Germany) has identified "237 ways that drones revolutionize business" and released a 151-page report consisting of 237 applications and 37 real-life case studies throughout 15 industries including agriculture, energy, construction, and mining.
The following is an incomplete list of some of those applications.
Aerospace.
Airlines and maintenance, repair, and operations contractors use UAVs for aircraft maintenance. In June 2015 EasyJet began testing UAVs in the maintenance of their Airbus A320s and in July 2016 at the Farnborough Airshow, Airbus (manufacturer of the A320), demonstrated the use of UAVs for the visual inspection of an aircraft. However, some aircraft maintenance professionals remain wary of the technology and its ability to properly catch potential dangers. 
In 2002, a paper was published suggesting autonomous robotic helicopters for Mars exploration, possible for the Mars Scout Program. A number of advantages of a viable rotorcraft design were noted, including the ability to pass over difficult Mars terrain yet still visit multiple sites "in situ". The short hop made by Lunar Surveyor 6 in 1967 was noted as example of hopping to visit another site.
A small scout drone, launching from a Mars rover has been in development in the late 2010s, including US$23 million for a helicopter demonstration in 2018. The program for the Mars Helicopter "Ingenuity" possibly for the "Perseverance" rover would have a high resolution, downward-looking camera for navigation, landing, and science surveying of the terrain, and a communication system to relay data back to the rover.
Drones on celestial bodies without atmosphere, like the Moon, have been proposed as drones reaching and sustaining above ground or sub-orbital flight through thrusters, creating the need for reaction mass.
Military.
UAVs are used by a broad range of military forces, from Argentina to the US and also by Islamic State of Iraq and the Levant (ISIS).
As of January 2014, the U.S. military operated 7,362 RQ-11B Ravens; 145 AeroVironment RQ-12A Wasps; 1,137 AeroVironment RQ-20A Pumas; 306 RQ-16 T-Hawk small UAS; 246 Predators and MQ-1C Grey Eagles; 126 MQ-9 Reapers; 491 RQ-7 Shadows and 33 RQ-4 Global Hawk large systems. The MQ-9 Reaper costs $12 million while a manned F-22 costs over $120 million.
ISIS announced a "Unmanned Aircraft of the Mujahideen" unit in January 2017 and use drones for both reconnaissance and to drop bombs.
Reconnaissance.
The Tu-141 "Swift" reusable Soviet reconnaissance UAV is intended for reconnaissance to a depth of several hundred kilometers from the front line at supersonic speeds. The Tu-123 "Hawk" is a supersonic long-range reconnaissance UAV intended for conducting photographic and signals intelligence to a distance of 3200 km; it was produced beginning in 1964. The La-17P (UAV) is a reconnaissance UAV produced since 1963. In 1945 the Soviet Union began producing "doodlebug". 43 Soviet/Russian UAV models are known.
In 2013, the U.S. Navy launched a UAV from a submerged submarine, the first step to "providing mission intelligence, surveillance and reconnaissance capabilities to the U.S. Navy's submarine force."
Turkish forces have used the Bayraktar Tactical UAS for reconnaissance during operations in northern Syria.
Attack.
UAVs avoid potential diplomatic embarrassment when a manned aircraft is shot down and the pilots captured.
MQ-1 Predator UAVs armed with Hellfire missiles have been used by the U.S. as platforms for hitting ground targets. Armed Predators were first used in late 2001, mostly aimed at assassinating high-profile individuals (terrorist leaders, etc.) inside Afghanistan.
Islamic State of Iraq and the Levant have used drones, adapting UAVs bought online, to drop explosives, primarily using quadcopters. Other groups in Syria are also thought to have used UAVs in attacks. A swarm of drones armed with bombs attacked Russian bases in western Syria in early January 2018.
Defense against UAVs.
The US armed forces have no defense against low-level UAV attack, but the Joint Integrated Air and Missile Defense Organization is working to repurpose existing systems. Two German companies are developing 40-kW lasers to damage UAVs. Other systems still include the OpenWorks Engineering Skywall and the Battelle DroneDefender.
In late 2017, Russia established a ground-based unit to combat UAVs by jamming their controlling signals. They used jamming and anti-aircraft fire to defend against a swarm attack in Syria in early January 2018.
ALKA is directed-energy weapon (DEW) system is a Turkish dual electromagnetic/laser weapon developed by Roketsan allegedly used to destroy one of GNC's Wing Loong II UAVs; if true, this would represent the first known time a vehicle mounted combat laser was used to destroy another combat vehicle during genuine wartime conditions.
Targets for military training.
Since 1997, the US military has used more than 80 F-4 Phantoms converted into UAVs as aerial targets for combat training of human pilots. The F-4s were supplemented in September 2013 with F-16s as more realistically maneuverable targets.
Demining.
Since January 2016 British scientists are developing UAVs with advanced imaging technology to more cheaply and effectively map and speed up the clearing of minefields. The Find A Better Way charity, working since 2011 to advance technologies that will enable safer and more efficient clearance of landmines, teamed up with scientists at the University of Bristol to develop UAVs fit with hyperspectral imaging technology that can quickly identify landmines buried in the ground. John Fardoulis, project researcher from Bristol University states that "the maps [their] UAVs will generate should help deminers focus on the places where mines are most likely to be found". Their intended UAVs will be able to perform flyovers and gather images at various wavelengths which, according to Dr John Day from the University of Bristol, could indicate explosive chemicals seeping from landmines into the surrounding foliage as "chemicals in landmines leak out and are often absorbed by plants, causing abnormalities" which can be detected as "living plants have a very distinctive reflection in the near infrared spectrum, just beyond human vision, which makes it possible to tell how healthy they are".
The Dutch Mine Kafon project, led by designer Massoud Hassani is working on a UAV system that can quickly detect and clear land mines. The unmanned airborne de-mining system called Mine Kafon Drone uses a three step process to autonomously map, detect and detonate land mines. It flies above potentially dangerous areas, generating a 3D map, and uses a metal detector to pinpoint the location of mines. The UAV can then place a detonator above the mines using its robotic gripping arm, before retreating to a safe distance. The firm claims its UAV is safer, 20 times faster and up to 200 times cheaper than current technologies and might clear mines globally in 10 years. The project raised funds on the crowdfunding site Kickstarter with their goal set at €70,000 and receiving over €100,000 above it.
Civil.
Civil uses include aerial crop surveys, aerial photography, search and rescue, inspection of power lines and pipelines, counting wildlife, delivering medical supplies to otherwise inaccessible regions, and detection of illegal hunting, reconnaissance operations, cooperative environment monitoring, border patrol missions, convoy protection, forest fire detection and monitoring, surveillance, coordinating humanitarian aid, plume tracking, land surveying, fire and large-accident investigation, landslide measurement, illegal landfill detection, the construction industry, smuggling, and crowd monitoring.
US government agencies use UAVs such as the RQ-9 Reaper to patrol borders, scout property and locate fugitives. One of the first authorized for domestic use was the ShadowHawk in Montgomery County, Texas SWAT and emergency management offices.
Private citizens and media organizations use UAVs for surveillance, recreation, news-gathering, or personal land assessment. In February 2012, an animal rights group used a MikroKopter hexacopter to film hunters shooting pigeons in South Carolina. The hunters then shot the UAV down. In 2014, a UAV was used to successfully locate a man with dementia, who was missing for 3 days.
Archaeology.
In Peru, archaeologists used UAVs to speed up survey work and protect sites from squatters, builders and miners. Small UAVs helped researchers produce three-dimensional models of Peruvian sites instead of the usual flat maps – and in days and weeks instead of months and years.
"You can go up three metres and photograph a room, 300 metres and photograph a site, or you can go up 3,000 metres and photograph the entire valley."
UAVs have replaced expensive and clumsy small planes, kites and helium balloons. UAVs costing as little as £650 have proven useful. In 2013, UAVs flew over Peruvian archaeological sites, including the colonial Andean town Machu Llacta above sea level. The UAVs had altitude problems in the Andes, leading to plans to make a UAV blimp.
In Jordan, UAVs were used to discover evidence of looted archaeological sites.
In September 2014, UAVs were used for 3D mapping of the above-ground ruins of Aphrodisias and the Gallo-Roman remains in Switzerland.
On 6 February 2017 it was reported that scientists from the UK and Brazil discovered hundreds of ancient earthworks similar to those at Stonehenge in the Amazon rainforest with the use of UAVs.
Cargo transport.
UAVs can transport medicines and medical specimens into and out of inaccessible regions. In 2013, in a research project of DHL, a small quantity of medicine was delivered via a UAV.
Initial attempts at commercial use of UAVs, such as the Tacocopter company for food delivery, were blocked by FAA regulation. A 2013 announcement that Amazon was planning deliveries using UAVs was met with skepticism.
In 2014, the prime minister of the United Arab Emirates announced that the UAE planned to launch a fleet of UAVs to deliver official documents and supply emergency services at accidents.
Google revealed in 2014 it had been testing UAVs for two years. The Google X program aims to produce UAVs that can deliver items.
16 July 2015, A NASA Langley fixed-wing Cirrus SR22 aircraft, flown remotely from the ground, operated by NASA's Langley Research Center in Hampton and a hexacopter UAV delivered pharmaceuticals and other medical supplies to an outdoor free clinic at the Wise County Fairgrounds, Virginia. The aircraft picked up 10 pounds of pharmaceuticals and supplies from an airport in Tazewell County in southwest Virginia and delivered the medicine to the Lonesome Pine Airport in Wise County. The aircraft had a pilot on board for safety. The supplies went to a crew, which separated the supplies into 24 smaller packages to be delivered by small, unmanned UAV to the free clinic, during multiple flights over two hours. A company pilot controlled the hexacopter, which lowered the pharmaceuticals to the ground by tether. Health care workers distributed the medications to appropriate patients.
The Uvionix Nksy aerial delivery service is planning to allow local shops to deliver goods from a UAV. The company wants to deliver fast food, beer, coffee, soda, electronics, prescriptions and personal care products.
Conservation.
In 2011, Lian Pin Koh and Serge Wich conceived the idea of using UAVs for conservation-related applications, before founding ConservationDrones in 2012. ConservationDrones works with NGOs, research organizations, and governments to collect environmental data through drone usage. They also work to provide low cost UAVs to these organizations, especially in developing countries, for as little as $2500. UAV usage in conservation is able to alleviate many of the challenges facing conservationists on foot, such as "the large size of species’ geographic ranges, low population densities, inaccessible habitat, elusive behavior and sensitivity to disturbance." By 2012 the International Anti-Poaching Foundation was using UAVs. A whale conservation UAV capable of collecting blowhole mucus into a sterile petri dish was put into use in January 2018 following its development by researchers at Macquarie University in Sydney, Australia.
UAVs have a particular role in anti-poaching activities. In June 2012, World Wide Fund for Nature (WWF) announced it would begin using UAVs in Nepal to aid conservation efforts following a successful trial of two aircraft in Chitwan National Park. The global wildlife organization planned to train ten personnel to use the UAVs, with operational use beginning in the fall. In August 2012, UAVs were used by members of the Sea Shepherd Conservation Society in Namibia to document the annual seal cull. In December 2013, the Falcon UAV was selected by the Namibian Government and WWF to help combat rhinoceros poaching. The UAVs will operate in Etosha National Park and will use implanted RFID tags.
In 2012, the WWFund supplied two FPV Raptor 1.6 UAVs to Nepal National Parks. These UAVs were used to monitor rhinos, tigers and elephants and deter poachers. The UAVs were equipped with time-lapse cameras and could fly for 18 miles at 650 feet.
In December 2012, Kruger National Park started using a Seeker II UAV