We see this world rich with culture, emotion, and human connections. The human built world can afford a sense of beauty, sublimity, and resonance, and through our advancements in technology also bringing the advancements in society. At the center of these advancements are interactions, conversations, connections, collaborations, and relationships, within and across multiple disciplines, with and without technology. For the last decades, as the computer technologies have been developing, the importance of human-computer systems interaction problems are also growing with the passage of time. This is not only because of the computer systems performance and characteristics have been improved, but also due to the growing number of computer users and of their expectations about general computer systems capabilities as universal tools for human work and life facilitation. Interface design is important for several reasons and the current growth of the different web applications are characterized by an increasing availability of online different services or products trading and different search facilities like flight search web sites, provided by most commercial airlines. In this study we will therefore create an understanding of the most important interaction design principles for the designers of online booking systems. The research methodology used in the research is design and creation. The method components used in this study are documents and interviews. The theoretical study has identified some important aspects covering the human computer interaction, usability of interactive interface, user feedback and the user-centered design approach for the development of such online booking systems. These aspects have been verified through the three interviews with the interviewees having different experience levels. The result shows that the interaction design is really important in designing of interactive online booking system. Therefore, the designers of such systems need to have an understanding of the most important design principles like the usability and functionality of the system, the approach should be iterative in design, provide proper feedback, minimum steps in booking process, risk management, and user-centered approach should be included in your design principles. It is also important for the designers of online booking systems to be aware of the usability factor of the system. The cognitive psychology is also vital for designers to understand how users think and perceive things. Designers need to have a good balance between context and graphics of the interface of such systems. The result also has been shown in the design of prototype with the most important interaction design principles and other factors. / Program: Magisterutbildning i informatik