Who is the call sign that has a commenced operation before 1976?
CREATE TABLE table_40674 (
    "AIRLINES" text,
    "IATA" text,
    "ICAO" text,
    "CALLSIGN" text,
    "COMMENCED OPERATIONS" real
)
SELECT "CALLSIGN" FROM table_40674 WHERE "COMMENCED OPERATIONS" < '1976'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: Who is the call sign that has a commenced operation before 1976? ### Input: CREATE TABLE table_40674 (
    "AIRLINES" text,
    "IATA" text,
    "ICAO" text,
    "CALLSIGN" text,
    "COMMENCED OPERATIONS" real
) ### Response: SELECT "CALLSIGN" FROM table_40674 WHERE "COMMENCED OPERATIONS" < '1976'