Here is a UML class diagram about how to book and airplane tickets in this system. UML, which stands for Unified Modeling Language, is one of the most popular ways of providing an in-depth visual representation for software development and engineering. Ideally, UML diagrams are associated with object-oriented programming languages like C++ or Java. It helps us provide an overall structure of the software and the flow of instructions. Learn more details from this diagram, or try to make yours with ease.