During the late 1970s and early 1980s, many people sought to fly affordably. As a result, many aviation authorities set up definitions of lightweight, slow-flying aeroplanes that could be subject to minimum regulation. The resulting aeroplanes are commonly called ultralight or microlight, although the weight and speed limits differ from country to country.
There is also an allowance of another 10% on Maximum Take Off Weight for seaplanes and amphibians, and some countries (such as Germany and France) also allow another 5% for installation of a ballistic parachute.
The safety regulations used to approve microlights vary between countries, the strictest being the United Kingdom, Italy, Sweden and Germany, while they are almost non-existent in France and the United States. The disparity between regulations is a barrier to international trade and overflight, as is the fact that these regulations are invariably sub-ICAO, which means that they are not internationally recognised.
In most affluent countries microlights or ultralights now account for a significant portion of the civil aircraft fleet. For instance in Canada the ultralight fleet makes up 18% of the total civil aircraft registered. In other countries that do not register ultralights, like the United States, it is unknown what proportion of the total fleet they make up.
In countries where there is no specific regulation, ultralights are considered regular aircraft and subject to certification requirements for both aircraft and pilot.
Ultralight aircraft are generally called microlight aircraft in the UK and New Zealand, and ULMs in France and Italy. Some countries differentiate between weight shift and 3-axis aircraft, calling the former microlight and the latter ultralight.
The U.S. light-sport aircraft is similar to the UK and NZ Microlight in definition and licensing requirement, the U.S. 'Ultralight' being in a class of its own.
Wikipedia:During the late 1970s and early 1980s, many people sought to fly affordably. As a result, m...