(OTT) refers to flying over top of clouds in visual flight, rather than with reference to instruments. This is usually done for brief amount of time to avoid weather or turbulence.
Each nation has specific and often different rules that govern when a pilot is permitted to fly VFR OTT. Most countries have requirements that specify weather minima, aircraft equipment and pilot qualifications.
In some countries pilots are required to get an Air Traffic Control (ATC) clearance, or in absence of a controller, advise the nearest Flight Service Station or Center.
Pilots are required to adhere to VFR minima when climbing and descending over the clouds. Flight in cloud is not permitted.
The rules for flying VFR OTT vary greatly from country to country. Some rules, such as those contained in the US Federal Aviation Regulations
, are quite simple to understand and easy to comply with. Others, such as the Canadian VFR OTT regulations contained in the Canadian Aviation Regulations
, are much more complex and more difficult to comply with.