Plural term for collective nouns

I understand that certain nouns (collective nouns?) that do not have a plural word. E.g. aircraft, rain and perspiration. However, I come across such usage, specially in Asia. "Many aircraftS are taking off and landing at this airport."  or "Beads of perspirationS fell from his forehead".
Are there actually such words as aircraftS and perspirationS?

Hvpl wrote:

I understand that certain nouns (collective nouns?) that do not have a plural word. E.g. aircraft, rain and perspiration. However, I come across such usage, specially in Asia. "Many aircraftS are taking off and landing at this airport."  or "Beads of perspirationS fell from his forehead". Are there actually such words as aircraftS and perspirationS?

Hello Hvpl

Welcome to this Forum. I too am an English learner from an East Asian country.

As for perspiration, my English-Japanese dictionary says "perspiration" is sometimes used as a countable noun, but I think that usage is very rare. Google gives 5,388,000 English pages for "perspiration" but only 16,000 pages for "perspiration". But there seems some people who say "profuse perspirations" on the analogy of "profuse tears".

"Aircraft" is commonly used as a collective noun but it is sometimes used as a countable nouns.
(EX) President Roosevelt said that the United States would build 6000 military aircraft.
(EX) The United States contemplated building an aircraft the size of a football field.
(EX) We made a decision to send aircraft -- heavy cargo aircrafts to help in the rescue operations.

paco

 "Aircraft" can be singular and plural forms for a countable noun "aircraft", but it also can behave like a collective noun.

paco