SQL & PL/SQL :: Creating A View In Developer SUM

I am having trouble with creating a view based on the following: -

Total hours flown EVER, for each crew of the FBN001 on 20th October 2011.

Here is what i got so far (only works for each members flown on a particular flight, NOT on their whole hours flown in a period of a lifetime) : -

SELECT e.Employee_Number, e.FirstName, e.LastName,
SUM( ( (s.ESTIMATED_ARRIVAL) - (s.ESTIMATED_DEPARTURE) )*24)AS
TOTAL_HOURS_FLOWN
FROM SCHEDULE s, CREW_ASSIGNMENT ca, EMPLOYEE e
WHERE
s.Flight_Number = ca.Flight_Number
AND
s.Serial_Number = ca.Serial_Number
[code]...