Airline companies around the world are experiencing increased costs in part due to .\

Threat of terrorism.

Explanation:

Airline companies around the world are experiencing increased costs in part due to threat of terrorism.

Safety is one of the most important factors that determine the cost of airline services around the world. To the averse risk of any mishappening during flight, airline companies take different measure and these measure cost lot of expenses, which result in increase in price of airfare. In recent days, the threat of terrorism is a major risk that the airline industry is facing, therefore, they are experiencing increase costs around the world.