Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_39805 ( "Airline" text, "ICAO" text, "IATA" text, "Callsign" text, "Commenced operations" real, "Fleet size" real, "Headquarters" text )

### Question ###
What is the of Fleet size with a IATA of pr, and a Commenced operations smaller than 1941?

### Accurate SQL ###

SELECT SUM("Fleet size") FROM table_39805 WHERE "IATA" = 'pr' AND "Commenced operations" < '1941'