UPDATE 5-Obama arrives in Havana for historic visit to Cuba
* Visit was unthinkable until Obama-Castro agreement
* Tight security and welcome signs await U.S. president
* No visit with Fidel Castro planned (Recasts with Obama arriving)
By Matt Spetalnick, Daniel Trotta, Jeff Mason and Frank Jack Daniel
HAVANA, March 20 (Reuters) - U.S. President Barack Obama arrived in Cuba on Sunday on a historic visit, opening a new chapter in U.S. engagement with the island's Communist government after decades of animosity between the former Cold War foes.
Obama landed at Havana's Jose Marti International Airport aboard Air Force One, the presidential jet with "United States of America" emblazoned across its fuselage, a sight almost unimaginable before the detente of December 2014.
The three-day trip, the first by a U.S. president to Cuba in 88 years, is the culmination of a diplomatic opening announced by Obama and Cuban President Raul Castro in December 2014, ending a Cold War-era estrangement that began when the Cuban revolution ousted a pro-American government in 1959.
Obama, who abandoned a longtime U.S. policy of trying to isolate Cuba, wants to make his shift irreversible. But major obstacles remain to full normalization of ties, and Obama's critics at home say the visit is premature.
Traveling with first lady Michelle Obama, her mother and their daughters, Sasha and Malia, the president will mostly play tourist on his first night on the Caribbean island, taking in the famous sights of Old Havana. Continuación...