The Requirement is a Database to support Aircraft Maintenance.
A. Part of the Business process includes these Steps :-
A.1 Customers submit Request For Quotations, (RFQs) online, and they are provided with Quotations.
A.2 Customers can prepare an Order based on the the quotation. 
A.3 There is only Vendor source for these Customers.

B. Things of Interest :-
B.1 Aircraft Parts
B.2 Customers
B.3 Orders
B.4 Quotations

C. How are they related ?
C.1 Customer can be associated with zero, one or many Quotations.
C.2 Customer can be associated with zero, one or many Orders.
C.3 An Order can be associated with zero, one or many Quotations.
C.4 A Quotation can be associated with zero, one or many Orders.