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People used to travel using air balloons although it was not very safe option in the beginning but it was efficient means of transport. There were no roads or quickest means of travel for people so they took a risk of traversing in the air using this heated air vessel. Helium and hydrogen were used later on as an improvement to the earlier design. The structure was very aerodynamic and it works on the principle of displacement of air. Many kinds of materials were used in the beginning, such as paper, plastic and even animal skin. The discovery of hot air balloons was accidental as people were traditionally used to flying sky lanterns. Nowadays, the technology is still used in remote areas where there are no roads built yet.