A global economic downturn negatively affects leisure, optional travel, as well as business travel. The price of fuel is now the greatest cost for many airlines and including a cost of maintenance and staff salaries. A plague or terrorist attack anywhere in the world can negatively affect air travel. The government intervention can result in new costly rules or unexpected new international competition. The climate can change all the time so the airlines have difficult to cope this problems such as the thunderstorm make the plane cannot take off.