The unmanned aerial vehicles (UAV, or drone) industry is the fastest growing aeronautics industry. Currently 50 countries use drones, three of them for military strikes.
The use of drones in US intelligence dates back to before World War II. They were also used in the Vietnam War like this scout drone, which was on display at Fort Myer, Virginia in 1960. Also known as the AN-USD-5, the UAV was 12 meters (36 feet) long and had an 8-meter wingspan.
Not all drones are used for military purposes. The Global Hawk is equipped with thermal imaging cameras and was deployed at Japan's damaged Daiichi nuclear power plant in Fukushima.
The SensoCopter weighs only 700 grams and is equipped with cameras for surveillance.
Drones are becoming smaller, lighter and more versatile. Here, a soldier launches a small unit remote scouting system, or SURSS drone.
While traditional drones were used for reconnaissance purposes, their descendants can be used in warfare. Here is a MQ-9 Reaper, armed with GBU-12 Paveway II laser guided munitions and AGM-114 Hellfire missiles, piloted by Colonel Lex Turner during a combat mission over southern Afghanistan.
UAVs have become popular among the US military, which is now thought to own over 7,000 of them. A decade ago it had 50. Drones are now being used in US military operations in Somalia, Yemen, Afghanistan, Pakistan, Iraq, Libya, Mexico and perhaps Mali soon. The X-47B Unmanned Combat Air System Demonstration (UCAS-D) aircraft can successfully take off from and land on an aircraft carrier.
The so-called 'kamikaze' Switchblade drone "is designed to provide the warfighter with a 'magic bullet'" and can "rapidly provide a powerful, but expendable miniature flying Intelligence, Surveillance and Reconnaissance (ISR) package on a Beyond Line-of-Sight (BLOS) target within minutes," according to its manufacturer AeroVironment.
Armed drones have become a main weapon in the 'War on Terror.' They are preferred for their precision and also because the technology allows strikes without endangering the lives of the soldiers operating them.
While technologies used in drones have become more complex and allow for better precision in attacks compared to traditional bombs, critics say a high number of civilians get killed or injured in UAV strikes.
The American Central Intelligence Agency (CIA) has maintained that drone strikes keep the number of civilian casualties at a minimum. Nonetheless, the UN has expressed interest in setting up a commission this year to investigate the legality of the use of armed drones in counter-terrorism operations.
There is increased criticism that drones cannot differentiate between intended targets and civilians. Campaigners say they breed anti-Americanism and terrorist recruitment. Here, protesters speak out against two US drone strikes in central Pakistan's Multan on January 8, in which eight people were said to have been killed.
Throughout the world, militaries are increasingly investing in drones programs. The US is a forerunner for its use of drones in the 'war on terror.'