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FAA call sign for the American Airlines flight carrying Pope Francis in the United States is "Shepherd One."

American Airlines is affixing the papal seal to the plane; has a long history of flying popes within the country.

Washington CNN  — 

The President flies on Air Force One. The Pope flies on “Shepherd One.”

That’s the Federal Aviation-approved call sign for the Boeing 777 in which he’ll be traveling around the United States, according to an official from American Airlines, which will be operating the plane.

The papal seal will also be affixed to the side of the aircraft, the only major modification that’s planned. However, the flight number will be blocked per a Secret Service request, so the public won’t be able to track its progress.

Once Francis wraps up his Washington visit and returns to Andrews Air Force Base on Thursday to head to New York, he’ll ditch the Alitalia jetliner he’s been on and pick up the American Airlines plane.

Air traffic control officials will use the name “Shepherd One” when speaking to the American Airlines captain flying the plane.

It’s become customary for the Pope to fly on and return home from official visits on the flag carrier of the country he has toured.

The Pope’s aircraft, chartered by the U.S. Conference of Bishops, will fly Francis from Andrews to John F. Kennedy International Airport in New York and then to Philadelphia International Airport before carrying the pope back to Rome at the end of his first U.S. visit.

American Airlines and TWA – which have merged – have a long history of carrying the Pope during visits to the United States. This trip will be the seventh time TWA and American Airlines have flown the Pope around the United States.

The plane that carried Pope John Paul II on one of those flights in 1993 – a Boeing 767-300ER operated by American Airlines – is still in operation. It’s scheduled to fly from Miami to Frankfurt, Germany, on Tuesday night.