The compound noun 'aircraft' (no space) is the same for both the singular and the plural form.
Examples:
An aircraft landed on the runway. (singular)
Several aircraft circled the field waiting to land. (plural)
Bridges is the plural form of bridge.
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
There is no plural form for the word, countries. This word itself is a plural.
The plural of "she" is "they", so the plural of "she had" is "they had".
There is no plural form of pupae. Pupae is the plural form of pupa.
The plural of aircraft is aircraft.One aircraft, two aircraft, ten aircraft.
Both the singular and the plural is aircraft.The plural possessive form is aircraft's.Example: All of the aircraft's inspections have been completed.
The noun 'aircraft' is an uncountable noun. The singular and the plural possessive form is aircraft's.EXAMPLESOne aircraft's owner has not paid the airport fee. (singular)All of these aircraft's owners are delinquent in their fees. (plural)
The plural of aircraft is aircraft. Much like how the plural of deer is deer. (Singular: That is such a beautiful aircraft / Plural: Look at all of those aircraft)
Some example nouns that are the same for singular and plural are:aircraftarchivesbinocularsbisonchalkdeerelkglassesheadquartersmoosenewsoffspringpajamaspantspolicereindeersalmonscissorsseriessheepspeciesswine
Aircraft is both singular and plural e.g. the pilot boarded his aircraft and took off; we watched as aircraft of all shapes and sizes filled the sky.
Examples of nouns that are the same in the singular and the plural:sheepdeergrouseChineseSwissLebaneseoffspringknowledgebarracksinformationbutterswine
Some examples of singular nouns that have the same form in both singular and plural are: sheep, deer, fish, aircraft.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."