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MIAMI (CBSMiami) – Pope Francis took off from Cuba Tuesday, headed for the United States where the biggest concern for his trip to three cities is safety.

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Earlier, Pope Francis celebrated a final mass with thousands of the faithful in Santiago De Cuba.  He called Catholicism the foundation of Cuban identity and called for a “revolution of tenderness” as Cubans rediscover their heritage.

Related: Pope Calls For “Revolution Of Tenderness”

Meantime, in Washington, D.C., crews were making final preparations for the pope’s arrival Tuesday afternoon.

The pontiff is scheduled to land at Joint Base Andrews, where he will be greeted by President Barack Obama and the first family.

Pope Francis’s arrival kicks off a six-day tour of the U.S., which includes several high-profile events in three of the nation’s largest cities.

The security plan has thousands of federal, state and local law enforcement assigned to watch over the pontiff, as well as the millions who want to see him.

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Security planners also studied every attempt on a pope’s life in the last 40 years.

“Not because we have specific information on a threat, but we wanted to remind everybody on these details in all three cities about the way these things have happened in the past, the different ways they’ve been put together,” said John Miller with the New York Police Department (NYPD).

The greatest concern is an attack by a “lone wolf.”

“No one can say with 100 percent certainty that you can stop everything, but there are steps you can take to minimize any opportunity for anyone to commit any kind of acts,” said Philadelphia Police Commissioner Charles Ramsey.

The pope will officially visit the White House Wednesday morning and will address a joint session of Congress on Thursday.

His last stop in the U.S. will be New York where he will address the United Nations General Assembly and hold a mass in Madison Square Garden.

Pope Francis will end his trip to the United States on Sunday night when he is set to head back to Rome.

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Click here for complete coverage of the pope’s visit.

Eliott Rodriguez