India, Sept. 11 -- Two hijacked planes cutting through the Manhattan sky into the World Trade Center, a plume of thick smoke rising above the Pentagon, and a shattered field in Pennsylvania: the images of September 11, 2001, remain burned into memory even a quarter-century later.

Nineteen al Qaeda terrorists hijacked four commercial aircraft 25 years ago on this day. They turned three of the planes into weapons against the World Trade Center in New York and the Pentagon near Washington. The fourth crashed into a field in Pennsylvania after passengers fought back.

The attacks killed 2,977 people, according to US government records. This figure excludes the 19 hijackers. The tragedy of 9/11, though, began long before the first plane hit....