WASHINGTON (AP) – Homeland Security Secretary Janet Napolitano says aviation is still the top terror target, 10 years after the 9/11 attacks.

Security enhancements at airports are among the most obvious changes since the attacks in 2001. New measures have gone in place as terrorsists have plotted new ways to try to bring down airliners.

Napolitano tells The Associated Press that the government sees more intelligence about threats to aviation than anything else.

Napolitano says she expects questions about whether the U.S. is safer than it was 10 years ago, as the country prepares to commemorate the 10-year anniversary of the attacks.

The answer, she says, is yes, the country is safer. But, she says, as the threat continues to change, there is not guarantee the country will not be attacked again.