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As a result, without radically increasing the cultivated area, a significant increase in crop yields was achieved; however, the rapidly growing populations of countries undergoing the industrial revolution needed ever more efficient agriculture. Large-scale food production became a profitable business. Mass cultivation, however, also meant a greater scale of the problem of pests, weeds and diseases. Large fields sown with a single crop species were at risk of disaster should a pest appear. Analogous problems arose in forestry, where due to industry demand, so-called monocultures were created, planting only single tree species (pine, spruce) in place of felled forests.

The plagues afflicting intensive agriculture required dynamic and wide-ranging countermeasures. When the aeroplane was built and perfected – a vehicle that was relatively fast and moved independently of terrain conditions – no special encouragement was needed to attempt to “harness wings to the plough.” After the enthusiast aviators, people looking for ways to put the invention to economic use became interested. Also in agriculture, for which the use of machines had become an important factor of development.

The first recorded case of pesticide spraying from an aeroplane was the dusting of catalpa trees in Ohio in August 1921, which took place on the initiative of the government and the United States Army. The aeroplane used was a Curtiss JN-6. Over the next two decades, the use of aircraft in agriculture gradually expanded. In 1922, aerial spraying trials were conducted in the USSR, and a few years later, U-1 (Avro 504) aircraft were used on a large scale to combat locusts in the northern Caucasus. Locusts were also fought from the air in the Philippines in 1924. In the 1930s, aircraft were also used for sowing in the USSR. In the 1920s, aircraft were also used to combat pests in Germany, Switzerland, Great Britain and France, while in New Zealand attempts were made to spread artificial fertilisers from an aeroplane. Aircraft also began to be used for fighting forest fires.

As a result of promising trials, the first organised agricultural aviation enterprises were established. The very first attempt in the USA was carried out by a public state institution in cooperation with the military. In 1923, influenced by the Ohio experience, the first private agricultural aviation company was founded – Huff Daland Dusters. Over time, this company expanded its services to include mail and passenger transport; initially there were no separate passenger aircraft, and a seat for 1 passenger was placed in… the chemical tank. Such were the modest beginnings of one of the largest American airlines – Delta Air Lines. In the USSR, the first agricultural aviation enterprise was established in 1930 and later incorporated into the Aeroflot structure.

Twin-engine C-47s, A-26s, and even heavy, four-engine B-24s gained a new role – having abandoned their destructive task, they began helping with food production and forest protection. However, light aircraft were best suited for agricultural tasks, such as the liaison-observation Piper L-4 Cub or the training Boeing PT-17 Stearman, N3N-3 and Polikarpov Po-2. A key role in the development of agricultural aviation was played by advances in chemistry and the creation of new crop protection products and artificial fertilisers. Products were developed whose application from the air was both economical and effective. Just as agricultural machinery before them, new chemical products gained popularity as a method of increasing crop yields.

With the growing agricultural aviation services market, the aviation industry undertook the design and production of aircraft fully specialised for agricultural work. The characteristic angular and humpbacked silhouettes of 2nd generation agricultural aircraft appeared over the fields. Agricultural aviation services were used in ever more countries. Upon gaining independence, many African states, lacking their own aviation industry and specialists, began using the agricultural aviation services of foreign companies; services were also commissioned by the United Nations. The international agricultural aviation market was developing.

Agricultural aviation techniques were used by the United States Air Force during the Second Indochina War (1964–75). Fighting the guerrilla tactics of the North Vietnamese Army, the USAF decided to use spraying techniques employed in agricultural aviation. Defoliants were applied – substances that cause plants to shed their leaves – in order to deprive the enemy of the cover provided by the lush vegetation of the subtropical zone, and of food obtained from local farmers. Between 1962 and 1971, Operation Ranch Hand was conducted, applying highly toxic “rainbow herbicides” on a large scale, including the infamous Agent Orange, in very high concentrations. They were produced by the same chemical corporations that supplied American and New Zealand agriculture.

These substances contained carcinogenic dioxins. The result of the operation was the destruction or damage of 22 km² of forests and croplands, and hundreds of thousands of people suffering from diseases and body deformities caused by contamination. Such massive use of agricultural aviation techniques in connection with an armed conflict has not been repeated; however, aerial spraying is used, for example, to destroy crops from which illegal drugs are produced, particularly in the case of plantations located in hard-to-reach places. Thus, military service did not bypass agricultural aircraft. Moreover, in some countries, firefighting flights are carried out by the air force, which for this purpose organises units equipped with agricultural aircraft. An example is the Hellenic Air Force (Polemikí Aeroporía), which uses Polish PZL M-18B Dromader aircraft.

People began to consider the possible undesirable effects of pesticide use – the death of beneficial insects and field birds, water contamination, cancers in people living in areas subjected to spraying and dusting. The most well-known example is DDT (in Poland also known as Azotox), a now somewhat forgotten insecticide whose name was once almost synonymous with environmental contamination. Intensive aerial fertilisation can also be harmful to the environment. For example, in New Zealand, where aerial fertilisation was widely used, algal blooms were observed in rivers into which fertilisers had leached, resulting in a decline in fish populations. This led to regulations that took into account the protection of water bodies during agricultural aviation operations.

Even the benefits of using aviation to extinguish burning forests are sometimes questioned by scientists, who point out that periodic fires have, in a broader perspective, a beneficial effect on the forest environment. The wave of controversy surrounding the chemicalisation of agriculture resulted in strengthened controls on chemicals used in agriculture and how they are applied. New regulations were introduced governing the permissibility and manner of use of chemicals for spraying and dusting, and the most dangerous substances were banned. Regulations were introduced specifying the weather conditions under which agricultural aviation operations can be conducted, so that, for example, spraying does not affect water bodies, environmentally valuable areas, or impact wildlife. As in every field of human activity, experience leads to better understanding and control of the consequences of our actions.

Even more widespread, though less intensive, is the use of flying vehicles in the service of forest protection, particularly firefighting. Many countries struggle with catastrophic forest fires. Flying machines, thanks to their range and speed of action, are indispensable in saving burning forests. This is, however, a difficult and exceptionally dangerous task (smoke, forests in mountainous terrain). The future will reveal the further career of wings over the fields.

Inventions may appear that undermine the rationale for conducting agricultural aviation work. For example, genetic modifications of plant traits (transgenic plants) may become an alternative and competitive method of crop protection compared to chemical treatments. Meanwhile, agricultural aviation remains an interesting and challenging type of aviation profession – one could say the most strongly connected to the earth. The history of agricultural aviation is a fascinating example of the use of modern technology in the oldest branch of the economy.