Howitt stresses, however, that while the nation demands retaliation, they must realize that “this is not the last time that this country will face a terrorist attack.”

Many Harvard experts predicted that increasing national security measures while maintaining Americans’ sense of freedom is one of the greatest challenges that lies ahead. The debate for how this must be accomplished centers on whether the attacks were the result of human error among security personnel or practical limitations of the system.

“I would hazard a guess that this was not a failure of physical security. So eliminating curb-side check-ins, better training for x-ray machine guards, bomb-sniffing dogs, and other proposed remedies are unlikely to prevent this sort of crime,” said Andrew Moravcsik, a government professor at the Center for European Studies.

Moravcsik said he advocates bolstering intelligence-gathering despite the fact that “Americans have traditionally eschewed such measures, which we associate with totalitarianism.”

Jim Walsh, a postdoctoral fellow in the Kennedy School of Government’s International Security Program, said the country’s response “should and must be driven by the facts of the case.”

“Every plan we consider must be weighed in terms of the costs to the United States, the cost of civilians, and the regional and political costs,” Walsh said. He stressed that there are a variety of options ranging from military action to basic law enforcement and that only time and the facts will deem which are appropriate.

Robert Rotberg, a lecturer in policy at the Kennedy School, said the nation must focus on prevention rather than revenge.

“A response of sending cruise missiles is more symbolic than affective,” he said. “We must and will make air traffic safer and this will change America as we know it.”