Question

what was the impact of the september 11th attacks on the tourism and travel industries?
costs increased because airlines had to build safer planes.
overall travel increased because people refused to be afraid.
revenue increased because more people traveled internationally.
costs increased because airlines had to improve security.

Explanation:

After the 9/11 attacks, airlines had to implement enhanced security measures like more screening, better - trained staff, and new security technologies, which led to increased costs. Travel did not increase overall immediately after the attacks due to fear and new restrictions. International travel also did not see an immediate increase in volume to boost revenue. Building safer planes was not the main cost - increasing factor right after the attacks; security enhancements were.

Answer:

D. Costs increased because airlines had to improve security.