After the terrorist attacks, the investigators discovered other targets like:
White House
Air Force one
Explanation:
After the terrorist attacks on the eleventh of September of two thousand and one, the investigators discovered that a plane that crashed in a field was going to the pentagon. However, they knew that there could have been more targets, the question was which element was another potential target. So, after they got the proper information from calls, and interrogatories they found out that the white house and the air force one were called "icons" and that they were strategically meaningful for the terrorists' plan. At some moment the statue of liberty was an "icon" but the terrorists wanted targets that could make the most damage to society including taking human lives. It all was discovered after the investigators identified the terrorists that kidnapped the planes and connections, they even captured suspects and interrogated them.
