America Under Attack: Anatomy of a collapse

South Tower | GIVING WAY
Weakened by the nearly 2,000-degree heat, the remaining columns buckle. The top portion slumps toward the damaged corner and rotates slightly.

Intro | North Tower |South Tower | Pentagon

GRAPHICS BY DOUG STERN - USN&WR
REPORTING BY AVERY COMAROW, DAVID LAGESSE, AND KENNETH TERRELL-USN&WR