Which of the following is not a difference between terrestrial aviation and space tourism as per the passage?

Directions: Read the passage and answer the question that follows:

Dennis Tito surprised the world when he paid $20 million to the Russian space agency to enjoy the adventure of the space flight. Some reporters denounced his profligacy while others eulogised his adventurous spirit. Whatever be the social or moral constraints, his private visit created sensation in the world. Many others also expressed their willingness to visit space and soon the agency got fully booked until 2009. Space tourism was once considered a dream of the lunatics. Today, however, it is no longer an outlandish vision from the realm of science fiction. The days are not far off when it would be a lucrative industry in the world of business. Several space tourism companies are planning to build suborbital vehicles and orbital cities within the next two decades. Very shortly, orbital flights will depart from many different airports and orbital facilities will grow, making space tourism popular and affordable. As in the case of tourism on Earth, there will be a small high-end segment for the rich, but the greater majority of space tourists will be middle class customers. Like any other business, once the industry gets started, it will develop progressively. It is now passing through high priced pioneering phase. After some years the prices are bound to get slashed as the number of tourists rise.

There are conservatives who say developing space tourism is very difficult and will take a long time. They also express their apprehensions and ask why would anyone want to go to orbit? There is nothing there, no air, no shops; it is just cold, dark nothing. But for those who have been to orbit, there are spectacular scenes of wonder, mystery and romance. In the space, stars do not twinkle, they are much brighter and closer and their colours are clearer.

Some companies are planning to build hotels in the space that could act as temporary space stations for the space tourists. The service will be nearer to adventure travel and orbital accommodation will be safe. Hotels in orbit would offer two unique experiences, splendid romantic view of the Earth and space, and the endless entertainment of living in zero gravity. It is a mind boggling experience of thrill and awe to look at the Earth from space and to enjoy weightlessness. Space walking will be another thrilling experience. The small gravitational pull created by the rotating space city would allow space tourists to walk around and function normally within the structure. Those who wish to stay longer in space can become passenger workers. Many producers of the Hollywood film industry are planning to shoot films in space; the space criminal stories, the space love stories will add new flavor and are likely to be box office hits.

Ironically few people are aware of how much work has been done to show that space tourism is a realistic goal and how the private companies are seriously engaged to boost space tourism industry. Space is no longer confined to research or military activities and the day is not far off when space tourism would become popular like the aviation industry; and equally affordable. It is estimated that by 2020 the space tourism will be as affordable as aviation flights.