#374 Air Balloons

In the past before the discovery of aeroplanes, people used to travel using hot air balloons. Although it was not a very safe option in the beginning, it was an [1] means of transport. There were no roads or quickest means of travel for people so they took a risk of [2] 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 [3] were used in the beginning, such as paper, plastic and even animal skin. The discovery of hot air balloon was [4] as people were traditionally used to flying sky lantern. Nowadays, the technology is so advanced and it is still used in the [5] areas where there are no roads built yet.