HAVANA – A U.S. replica of the 19th-century Cuban slave ship "Amistad" glided through the millpond-calm waters of Havana Bay on Thursday, a reminder of the countries' intertwined past and a gesture toward a brighter shared future.

Built in Connecticut, the black-hulled, two-masted re-creation of the schooner, whose name means "Friendship," flew the American and Cuban flags — as well as the blue flag of the United Nations. It was one of the few times a ship under the Stars and Stripes has called on the island in 51 years of estrangement since Fidel Castro took power. As it neared shore, the crew of 19 Americans lowered the U.S. flag and ran Cuba's up the main mast.

It feels like a promise fulfilled," said Gregory Belanger, the CEO and president of Amistad America Inc., the nonprofit organization that owns and operates the ship. "It was built here originally. Its sail is from here. Now it is here.

U.S. movie director Steven Spielberg made the story of the original Amistad famous with his 1997 film of the same name. The ship set sail from Havana carrying a cargo of captives from Sierra Leone in 1839. The Africans rebelled, commandeering the ship on a zigzag course up the U.S. coast until it was finally seized off the coast of Long Island.

The captured Africans became an international cause for abolitionists, and their fate was finally decided in 1841, when John Quincy Adams argued their case before the Supreme Court, which granted them freedom.

It was an inspirational ending to an otherwise sinister historical period — and some who helped bring the Amistad replica to this country hope its simple arrival could signal hope for improving a half-century and counting of frigid U.S.-Cuba relations.

If one of the two sides, either the U.S. or Cuba, had not wanted this to occur it wouldn't have," said Steve Schwadron, a consultant on the Amistad project and former chief of staff for Rep. William Delahunt. The Massachusetts Democrat has long worked to ease U.S.-Cuba relations and reached out to the State Department to make officials aware of the Amistad's proposal.

Thursday commemorates the day, March 25, 1807, when the British Parliament outlawed the slave trade. It also marks the 10th anniversary of the replica's rechristening. As the Amistad took to the seas a decade ago, its builders at Connecticut's Mystic Seaport vowed to get it to Cuba's capital or bust.

It first arrived on the island Tuesday at the port of Matanzas, 60 miles (95 kilometers) east of Havana. Thursday's mostly calm, blue-gray waves made for smooth sailing past the Morro Castle, a Spanish fort built in 1859 that guards the sea entrance to Havana. The Amistad then hugged the storied waterfront, passing the iconic Hotel Nacional before reaching a modern cruise ship port on the edge of the city's historic harbor district.

Using high technology hidden in its wooden frame and rigging, the new Amistad has crossed the Atlantic and wended its way through the Caribbean since 2007 as part of the United Nations and UNESCO's Slave Route Project.

The ship will offer public tours, remaining for six days near the warren of narrow, cobblestone streets and gracefully decaying homes and apartment buildings with colonial-era courtyards and terraces that comprise Havana's historic district.

Cuba's state television re-aired the Spielberg film this week. Officials anticipate so many visitors to the ship that they asked the Amistad to add extra hours when it will be open to the public.

On Friday, an educational simulcast will link high schoolers in Havana to an auditorium of 300 students at U.N. headquarters, as well as youngsters who have studied the real Amistad in Gambia, the United Kingdom, Trinidad and Tobago, Guyana and Jamaica.

Many believed the administration of President Barack Obama could lead a reconciliation effort with Cuba. But the ship arrived as international tension over the island's human rights record has intensified since the Feb. 23 death of dissident Orlando Zapata Tamayo after a long prison hunger strike.

Obama said Wednesday that Zapata Tamayo's death was "deeply disturbing" and shows that, instead of entering a new era, Cuban authorities continue to respond to the aspirations of its people with a clenched fist.

On the same day the ship was docking in Havana, pop icon Gloria Estefan was leading a march in support of a top Cuban dissident group through the streets of Miami's Little Havana neighborhood.

From Cuba, the Amistad will head up the U.S. East Coast with a stop in Washington, and remain in U.S. waters until August, telling the tale of its stop in Cuba all along the way, Belanger said.

Washington has periodically approved Cuba stops for semester-at-sea educational programs for American students, and authorized U.S. shiploads of exports under agriculture and medical exemptions to the 48-year-old U.S. trade embargo against the island.

The Amistad required permission from the U.S. Treasury and Commerce Departments to make the voyage — authorization that did not always appear it would be forthcoming.

There isn't a license category for a 19th-century slave ship," Schwadron joked.