Airlines have several employees. The system modeled needs to keep track of the names and birth dates of all employees of airlines, which are identified by their names. Each of the airline employees can be employed by more than one airline at any given point in time, and the start-date for each of these employments are modeled. Captains and flight attendants are the only type of employees we are interested in modeling in this system. Airlines have several flights that are stored as flight descriptions. A flight number uniquely determines a flight description. A flight description corresponds to an ordered set of several flights. A flight has several flight attendants but only one lead attendant. Each of these flight attendants, including the lead attendant, is associated with several flights. A flight has only one captain and each of these captains pilot several flights over a period of time