While certainly an open-ended question that you are free to take in multiple directions, it is important that you carefully read the British Airways job description prior to your interview to be able to talk about the two or three main responsibilities of a flight attendant with the airline. Talk to the interviewer about what you feel is most important to achieve on a day-to-day basis and try to focus your answer on the fact that providing excellent customer service is always the first priority in this role.