What is the average departure delay time of flights operated by American Airlines Inc.?
average departure delay time = DIVIDE(SUM(DEP_DELAY), COUNT(Code)); American Airlines Inc. refers to Description = 'American Airlines Inc.: AA';
SELECT AVG(T1.DEP_DELAY) FROM Airlines AS T1 INNER JOIN Airports AS T2 ON T2.Code = T1.ORIGIN INNER JOIN `Air Carriers` AS T3 ON T1.OP_CARRIER_AIRLINE_ID = T3.Code WHERE T3.Description = 'American Airlines Inc.: AA'
CREATE TABLE IF NOT EXISTS "Air Carriers"
(
    Code        INTEGER
            primary key,
    Description TEXT
);
CREATE TABLE Airports
(
    Code        TEXT
            primary key,
    Description TEXT
);
CREATE TABLE Airlines
(
    FL_DATE               TEXT,
    OP_CARRIER_AIRLINE_ID INTEGER,
    TAIL_NUM              TEXT,
    OP_CARRIER_FL_NUM     INTEGER,
    ORIGIN_AIRPORT_ID     INTEGER,
    ORIGIN_AIRPORT_SEQ_ID INTEGER,
    ORIGIN_CITY_MARKET_ID INTEGER,
    ORIGIN                TEXT,
    DEST_AIRPORT_ID       INTEGER,
    DEST_AIRPORT_SEQ_ID   INTEGER,
    DEST_CITY_MARKET_ID   INTEGER,
    DEST                  TEXT,
    CRS_DEP_TIME          INTEGER,
    DEP_TIME              INTEGER,
    DEP_DELAY             INTEGER,
    DEP_DELAY_NEW         INTEGER,
    ARR_TIME              INTEGER,
    ARR_DELAY             INTEGER,
    ARR_DELAY_NEW         INTEGER,
    CANCELLED             INTEGER,
    CANCELLATION_CODE     TEXT,
    CRS_ELAPSED_TIME      INTEGER,
    ACTUAL_ELAPSED_TIME   INTEGER,
    CARRIER_DELAY         INTEGER,
    WEATHER_DELAY         INTEGER,
    NAS_DELAY             INTEGER,
    SECURITY_DELAY        INTEGER,
    LATE_AIRCRAFT_DELAY   INTEGER,
    FOREIGN KEY (ORIGIN) REFERENCES Airports(Code),
    FOREIGN KEY (DEST) REFERENCES Airports(Code),
    FOREIGN KEY (OP_CARRIER_AIRLINE_ID) REFERENCES "Air Carriers"(Code)
);
