ORA-00904: "S"."AIR_TIME": invalid identifier

Question

Why does this code show invalid identifier when sum is used in distance and air_time column? When sum is not used this statement process successfully but using sum I get error? I need to use sum for this statement.

 MERGE INTO FACT_COMPANY_GROWTH F
    USING (SELECT DISTINCT TIME_ID, FLIGHT_KEY, AEROPLANE_KEY, SUM(DISTANCE) AS TOTAL_DISTANCE, SUM(AIR_TIME) AS TOTAL_AIRTIME
    FROM TRANSFORM_FLIGHT T
    INNER JOIN TRANSFORM_AEROPLANE A
    ON T.FK_AEROPLANE_KEY = A.AEROPLANE_KEY
    INNER JOIN DIM_TIME D
    ON D.YEAR = T.YEAR
    AND D.MONTH = T.MONTH
    GROUP BY TIME_ID, FLIGHT_KEY, AEROPLANE_KEY) S
    ON (F.FK1_TIME_ID = S.TIME_ID
    AND F.FK2_FLIGHT_KEY = S.FLIGHT_KEY
    AND F.FK3_AEROPLANE_KEY = S.AEROPLANE_KEY
    ) 
    WHEN MATCHED THEN
    UPDATE SET
    F.TOTAL_AIRTIME = S.AIR_TIME,
    F.TOTAL_DISTANCE = S.DISTANCE,
    F.TOTAL_NO_OF_FLIGHTS = S.FLIGHT_KEY,
    F.TOTAL_NO_OF_AEROPLANE = S.AEROPLANE_KEY
    WHEN NOT MATCHED THEN
    INSERT(FACT_ID, FK1_TIME_ID, FK2_FLIGHT_KEY, FK3_AEROPLANE_KEY, TOTAL_DISTANCE, TOTAL_AIRTIME, TOTAL_NO_OF_FLIGHTS, TOTAL_NO_OF_AEROPLANE)
    VALUES
    (NULL, S.TIME_ID, S.FLIGHT_KEY, S.AEROPLANE_KEY, S.DISTANCE, S.AIR_TIME,  S.FLIGHT_KEY, S.AEROPLANE_KEY);

Answer 1

UPDATE SET
    F.TOTAL_AIRTIME = S.TOTAL_AIRTIME,
    F.TOTAL_DISTANCE = S.TOTAL_DISTANCE,

Answer 2

USING(
    SELECT DISTINCT 
        TIME_ID, 
        FLIGHT_KEY, 
        AEROPLANE_KEY, 
        SUM(DISTANCE) AS TOTAL_DISTANCE, 
        SUM(AIR_TIME) AS TOTAL_AIRTIME
...) S

The problem is at UPDATE SET F.TOTAL_AIRTIME = S.AIR_TIME. There are 5 fields defined in S and none is named AIR_TIME.