We can reduce our travel time significantly if we travel by an aeroplane. But it comes with a cost—both financial and environmental. Aircraft engines emit noise and gases such as carbon dioxide, carbon monoxide and black carbon. These can all cause global warming. As per the Department of Science and Technology of India, it is uncertain if black carbon released from aircrafts has an impact on the monsoon, glaciers and the ozone layer, but studies have shown that it can reach the stratosphere and warm the atmosphere at that level.