Draw an entity-relationship diagram for the following case.

Superior Aircraft, Inc., is a passenger airplane manufacturer. It manufactures airplanes at its factory in Memphis, TN, and is responsible for the maintenance of the airplanes it manufactures. Maintenance operations are performed at ten maintenance shops that are located in various cities in the US and abroad. Superior wants to design a new information system to maintain records about its airplanes and its manufacturing and maintenance operations.

Each airplane is identified by a unique serial number. In addition, Superior wants to record each airplane's model, date-of-manufacture (the date it was finished), and passenger capacity. Superior deals with many suppliers that supply parts for its airplanes. Each supplier has a unique company name, the address of its headquarters, and its telephone number. Each part has a serial number that is only unique within the company that made it. Superior also wants to record the type of part and the date that its manufacturing was completed. A supplier manufactures many parts. Obviously, each airplane requires many parts.

Each of the ten maintenance shops are identified by their location name (e.g. New York Shop.) The system must also store their address and the name of the site manager. Over time, an airplane can have maintenance performed on it at different locations. Each time a maintenance operation is performed on an airplane the system must record the date and the type of operation.

Superior assigns each of its employees an employee number. The system must also store an employee's name, date-of-hire, and a list of their skills. Some employees supervise other employees. During the manufacture of an airplane, the system records the date and the operation that an employee performed on the airplane being built. In order to build and maintain their skills, each employee must periodically take training courses, but a new employee may not have taken any courses, yet. Each course has a course number, name, and level (e.g. intermediate, advanced, etc.)

Superior must also keep track of the airline that bought each airplane that it manufactured. (Assume that once an airline buys a plane, it keeps it forever.) Airline names are unique. The system must record the date that an airline acquired an airplane and the amount that it paid for it.