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An alternate to this scheme is currently drafted atWikipedia:WikiProject Aircraft/Categories/Proposed update.

1. Top-level categories, such asCategory:Aviation andCategory:Aircraft, should not be populated. (Their category pages can be marked with the{{catdiffuse}} template.) Specific subcategories should be used such asCategory:United States airliners 1940–1949.
2. Articles should not generally be in both a category and a subcategory of it. For example, do not put someone in bothCategory:Canadian airliners 1990–1999 andCategory:Canadian aircraft 1990–1999, because the first is a subcategory of the latter. (For exceptions to this rule seeSUBCAT.)

The category scheme originates in one root category—Category:Aviation—and can be thought of as atree structure. A guide to the top-level sub-categories of this category is presented below; for brevity, a number of categories that are rarely used or lie outside the scope of this project have been omitted.

Category:Aviation

Root category for matters related to aviation. This category should be empty of articles,

Category:Aerobatics

Root category for all topics related to aerobatics.

.....

A number of naming conventions exist specifically for category names; most of these are used to ensure consistent naming among all the sub-categories of a particular category.

"X by country"

In most cases, sub-categories of a category named "X by country" take names of the form "X of [the] Y", where Y is the most common name of the country in question. For example:

• Category:Aviation by country → "Aviation in [the] Y" (as inCategory:Aviation in Canada)
• Category:Aircraft by country → "Aircraft manufactured by of [the] Y" (as inCategory:Aircraft manufactured by Israel)
• Category:Airlines by country → "Airlines of [the] Y" (as inCategory:Airlines of the United States)
• Category:Airports by country → "Airports in [the] Y" (as inCategory:Airports in Australia)
• Category:Aviation accidents and incidents by country → "Aviation accidents and incidents in [the] Y" (as inCategory:Aviation accidents and incidents in Germany)

"X by period"

In most cases, sub-categories of a category named "X by period" take names of the form "X Y", where Y is the name of the period of the subject in question. For example:

• Category:Aircraft by period → "Aircraft Y" (as inCategory:Aircraft 1900-1909)
• Category:Airlines by year of establishment → "Airlines established in Y" (as inCategory:Airlines established in 1958)

"X by type"

In most cases, sub-categories of a category named "X by type" take names of the form "Y X", where Y describes the type in question. For example:

• Category:Aircraft by type → "Y aircraft" (as inCategory:Hypersonic aircraft)
• Category:Airports by type → "Y airport" (as inCategory:Defunct airports)

Note that this form of category tree tends to exhibit more varied naming than the others. For example,Category:Aircraft by type also includes the non-standardCategory:Airliners (since "Airliner aircraft" would be a cumbersome name).

Intersection categories

The names ofintersection categories generally follow the same conventions as above, with the name components of their parent categories placed in normal grammatical order (usually with era givenafter country). This produces, for example, "Canadian aircraft 1960-1969" (country and era) and "Canadian military trainer aircraft 1930-1939" (country, type, and era).

In general, articles and categories should be placed in themost specific applicable categories, and should not be placed directly in a "parent" category if they are already present in one of its sub-categories. In other words, if an article is placed inCategory:United States airliners 1940-1949, there is no need to place it inCategory:United States civil aircraft 1940-1949 orCategory:Aircraft manufactured by the United States as well.

Note, however, that this applies only todirect placement into a "parent" category; it is normal for a category to have multipleindirect paths up to some other category higher in the tree. For example,Category:United States military transport aircraft 1940-1949 is both a sub-category ofCategory:Military transport aircraft 1940-1949 (which is a sub-category ofCategory:Military aircraft 1940-1949) and a sub-category ofCategory:United States military aircraft 1940-1949 (which isalso a sub-categoryCategory:Military aircraft 1940-1949); thus, there are two distinct paths fromCategory:United States military transport aircraft 1940-1949 up toCategory:Military aircraft 1940-1949. This is especially common when dealing withintersection categories.

This sectionneeds expansion. You can help byadding missing information.(July 2009)

This sectionneeds expansion. You can help byadding missing information.(July 2009)

This sectionneeds expansion. You can help byadding missing information.(July 2009)

This sectionneeds expansion. You can help byadding missing information.(July 2009)

Airport articles should include the most specific category possible based on location. Eachcountry has its own airport category, which can be found atCategory: Airports by country (also available grouped bycontinent atCategory: Airports by continent). For example,Copenhagen Airport in Denmark includesCategory: Airports in Denmark.

Some larger countries have sub-categories for first leveladministrative divisions, such asstate orprovince. These can be found under the country's airport category and should be used where available. For example,Québec City Jean Lesage International Airport in theCanadian province of Quebec includesCategory: Airports in Quebec, a sub-category ofCategory: Airports in Canada (which is not added to the article).

Airport articles often include a location category for an administrative division below that of the airport category. For example,Nice Côte d'Azur Airport in Nice, France, includes bothCategory: Airports in France andCategory: Nice.

Besides the location related categories, some airport articles may include other categories, such as those listed atCategory: Airports by type. For example,Independence State Airport in theU.S. state of Oregon includesCategory: Residential airparks in addition toCategory: Airports in Oregon andCategory: Polk County, Oregon.

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