Hartsfield-Jackson Atlanta International Airport
O'Hare International <span>Airport
Dallas-Fort Worth International
Airport Denver International Airport
Los Angeles International Airport. </span>
Almost 3000 people died directly from the attacks (the official number, which includes the attackers) is 2996.
However, the actual death toll connected to the attack indirectly is bigger and it's harder to asses, as it lead to the US military actions in the middle East, searching for Osama Bin laden.
It is marginal cost. <span>the marginal cost is the cost of making one more, and the marginal benefit is the price received from selling one more.</span>