Civil aviation is one of two major categories of flying, representing all non-military aviation, both private and commercial. Most of the countries in the world are members of the International Civil Aviation Organization (ICAO) and work together to establish common standards and rules for civil aviation through that agency -- the most notable exception is the United States, which does not belong to ICAO but has still worked to harmonize its regulations and procedures to avoid confusion for pilots flying to and from other countries.

Because civil aviation and military aviation operate under different rules around the world, there are sometimes difficulties when the two share the same airspace, occasionally with fatal results.

Civil aviation includes two major categories:

• Scheduled air transport, including all passenger or cargo flights that operate on a published schedule; and
• General aviation, including all other flights, private or commercial

For the public, the most visible part of civil aviation is scheduled air transport, but in fact, the vast majority of flights operate under general aviation.