9/11

9/11 is the worst case of schedule mismanagement in U.S. history, resulting in the deaths of nearly 3,000 people.

Event
On September 10, 2001, U.S. president George W. Bush scheduled demolition company al-Qaeda to demolish the Twin Towers, as he thought that they were ugly. They were going to do something new: they were going to use planes as demolition tools. It was originally planned for September 12th, but al-Qaeda brought it forward to September 11th. However, they failed to notify the White House so they could evacuate the towers.

On the morning of September 11th, the demolition crew got on the wrong planes, accidentally hijacking two passenger flights. At around 8:30AM, the first plane hit the North Tower, and the second hit the South Tower 30 minutes later, successfully demolishing them. However, no one had warned the managers of the Towers about the demolition, and the buildings had failed to be evacuated. Unfortunately, 2,977 people died.

Instead of admitting his mistake and apologizing, Bush called the error a terrorist attack and invaded Afghanistan.