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 September 11th attacks, airlines had to significantly enhance security measures which led to increased costs. Building safer planes was not the main cost - driver immediately after the attacks. Overall travel decreased due to fear and new security regulations, not increased. Revenue did not increase as fewer people were traveling.

Answer:

Costs increased because airlines had to improve security.