My first reaction to aircrafts was to think it was a typo, but I just checked usage on NGrams... ...and compared it to usage for the singular / collective noun form aircraft... ...which seems to ...
Is there a term for nouns that have identical singular and plural forms? For example, sheep fish glasses aircraft/spacecraft etc.
Why do some nouns in English not take the plurality suffix in the plural form? Could you give me a list of plural nouns which don't take "-(e)s" suffix? For example, I know about "fish" and "sheep".