An advisory circular is a term that describes a written communication that is aimed at a group of related commercial businesses or governmental departments. Generally, an advisory circular contains guidelines on how to manage with changes to previous working practices or how to interpret existing regulations. These advisory guidelines are generally not binding but are for information purposes only. They may be mailed or e-mailed to a list of relevant people or available on the Internet for a price or for free.
The term is often used in the context of transport and aviation. This type of communication often arises from a governmental regulatory authority because they control the rules in relation to airspace and transportation. For example, the United States Federal Aviation Authority (FAA) circulates "Advisory Circulars" to relevant aviation businesses. They keep a mailing list on computer with the names and addresses of the operators that need to know the correct manner in which to interpret new regulations.
As they are important for general safety behaviors in the areas of transport and aviation, issuing authorities may post advisory circulars on the official website for free access. Operators who wish to get the information may also be able to order several paper copies of the advisory circular for free, but bulk copies may incur a charge. Some advisory circulars need to be paid for individually before being sent out. Another option for dissemination of advice is to publish the circulars as a subscription service, where the customer has to pay for a certain period, such as a year, during which time he or she receives all the approved advisory circulars.
Businesses outside of aviation and transport may also issue advisory circulars. In any case where a rule or regulation needs some clarification, the business can disseminate this clarification through a nonbinding advisory circular. These communications originate from the top levels of relevant departments, where the decisions are made.
Generally, an advisory circular deals with clarification of one particular change in regulations. The circular is merely advice on how to deal with a particular situation, and it need not necessarily be followed to the letter. More than one advisory circular can be released by authoritative bodies on readjustments of the regulations, and as they are typically numbered for easy cross-referencing, relevant circulars are easy to find by interested parties. This referencing system also allows a customer to order the right circular for his or her purposes. This may also be possible for old circulars as well as new advisory communications.