At 542 mph near sea level, Flight 175 was pushed to the very edge of in-flight structural failure. But the hijackers didn't need precise control to hit a 110-story billboard.
Striking the World Trade Center at such extreme speeds was possible due to pristine weather, enormous targets, and basic visual navigation. On the morning of September 11, 2001, visibility over New York was perfect. The hijackers did not rely on complex instruments to find their targets. American Airlines Flight 11 hit the North Tower at an estimated 443 mph, while Flight 175 struck the South Tower at 542 mph. By following obvious geographical landmarks—specifically the Hudson River—they oriented themselves from dozens of miles away.
Once aligned with Manhattan, the targets were impossible to miss. The Twin Towers each had a footprint 208 feet wide and stood over 1,360 feet tall. Standing completely unobstructed above the rest of the skyline, they dominated the horizon from the cockpit of an approaching aircraft. At 500 mph, an aircraft travels about 730 feet per second. Once a pilot points the nose of the aircraft at a structure that wide from a few miles out, hitting it simply requires holding the yoke steady.
The physics of the low-altitude flights made control difficult, though not impossible. Dense air near sea level exerts massive aerodynamic forces on a Boeing 767. At 500 mph, flight controls stiffen severely. The approach to the South Tower was particularly erratic. United Airlines Flight 175 approached from the south, executing a rapid descent followed by a sharp lateral adjustment. The aircraft struck the building while banked at 38 degrees. Aviation investigators noted that this aggressive, high-speed maneuver left almost zero margin for error, with the airframe operating at its absolute physical limits just seconds before impact.