Mystery of Flight 455: Forty years on questions remain about whether the CIA was behind the bombing of a Cuban passenger jet in which 73 people died

• e-mail

Forty years ago today a Douglas DC-8 aircraft trundled down the runway at Grantley Adams International Airport in Barbados and took off, climbing into a blue Caribbean sky.

As Flight 455 reached 18,000 feet, a bomb went off under an empty seat, the plane's ascent slowed and it began to bank dangerously. 

Eight minutes later a second bomb went off in the toilet at the back of the plane and the plane plunged into the ocean.

Everyone on board perished. 

This memorial overlooking the ocean in Barbados is a reminder of the tragedy 40 years ago. But who was behind the bomb remains a mystery

Among them were the 73 people on board were a girl aged nine and all 24 members of Cuba's national fencing team, who had won the world championships the previous year.

It was, at the time, the worst terrorist atrocity in the western hemisphere. 

But 40 years later the full truth has yet to emerge about who was to blame for the disaster. 

A diver lifts wreckage from Flight 455 onto a boat off the coast of Barbados in 1976

The plane was owned by Cubana de Aviación, the state-owned airline of Fidel Castro's Cuba, and suspicions immediately turned to his political opponents and their CIA backers.

Two Venezuelan nationals, Hernán Ricardo and Freddy Lugo were later convicted of their involvement in the bombing and jailed for 20 years.

They had boarded the plane in Caracas, Venezuela, and planted the time bombs before disembarking in Barbados.

Luis Posada Carriles is an old man now (right) but at the time of the bombing he was a young (left) who was prominent in the CIA-backed anti-Castro movement

Ricardo was paid $25,000 (£20,000) for his part in the atrocity and after his release from prison he reportedly moved to Florida and worked undercover for the US Drug Enforcement Administration (DEA).

But the Venezuelans were only part of a wider plot.  

Two Cuban exiles, who despised the Castro regime, are believed to have planned it.

Orlando Bosch died in 2011, aged 84, but Luis Posada Carriles, 88, is alive and well and living in the US.

Posada Carriles was a CIA agent who had taken part in the failed Bay of Pigs invasion of Cuba and retained close links with anti-Castro elements in Florida.

Cubans youth hold up dozens of photos of people who Havana claims are victims of US aggression, including the passengers on Cubana Flight 455, which was blown up in 1976

He was jailed in Venezuela for his role in the bombing of Flight 455 but escaped from jail in 1985 and was later jailed in Panama for plotting the assassination of Fidel Castro.

Relations between the US and Cuba, which were frozen solid during the Cold War and for decades afterwards, have started thawing after President Barack Obama's historic announcement in December 2014.

Obama visited Havana earlier this year - the first by a US President in more than half a century- and last week he appointed Jeffrey DeLaurentis to be the first US ambassador to Cuba in 55 years.

But Flight 455 is one of a number of obstacles in the way of better relations.

The Cubans are demanding to know whether the CIA was involved and protesters often march through Havana with photographs of the dead. 

The plane was returning to Cuba, via Barbados and Jamaica, after the Pan American Games in Caracas, where the Cuban fencing team had just won gold medals.

Also on board were five North Koreans and 11 people from Guyana, including a girl aged nine. 

Cuban President Raul Castro raises President Obama's hand during his visit to the island earlier this year. Donald Trump wants to kill Obama's Cuba initiative stone dead and go back to the years when the two countries were virtually at war

The airport serving the Barbadian capital, Bridgetown, had only recently been renamed after former prime minister Grantley Adams and was still known as Seawell to most pilots. 

Air controllers said the pilot, Wilfredo Pérez, reported an emergency on board soon after take off: 'Seawell, Seawell! CU-455, Seawell...we have an explosion on board...we have a fire on board.'

Dalton Guiller watched the disaster from his boat off the coast of Barbados and told Venezuelan attorney Jose Pertierra: 'It didn't look right. It was too low. 

'I then saw the plane rise slightly, bank to the right and crash into the water: nose and wing first.'

He said he steered his boat to the site where he saw the plane came down and he said: 'I saw suitcases, seats, and personal effects. I saw bodies, only one or two of them intact. The others were not full bodies.'

A Cuban diver goes into the waters off Barbados searching for wreckage from the plane in October 1976

The United States has never admitted any involvement in the fate of Flight 455, let alone apologised for it. 

Mr Posada Carriles - who is also wanted by Venezuela in connection with the bombing of Flight 455 - went on trial in Texas in 2011 but, after a trial lasting 13 weeks, the jury acquitted him on 11 counts of perjury and immigration fraud.

He had been accused of lying to immigration officials about how he got into the US and about his involvement in bomb attacks in Havana in 1997 in which an Italian tourist was killed. 

His lawyer told a federal court judge his client admitted taking part in death squads in El Salvador and blowing up a university in Panama but said all his actions in Latin America were 'in the name of Washington'.

The State Department and the CIA have been contacted by Mail Online but have not responded to requests for interviews. 

The Cuban Foreign Ministry has also not commented. 

WHY US/CUBA RELATIONS COOLED DOWN AND ARE NOW WARMING UP 

Some of the 125,000 refugees who were allowed to leave Cuba in May 1980 in the Mariel boatlift, named after the port from which most of them left

In March 2016 Barack Obama became the first US president to visit Cuba since Calvin Coolidge in 1928.

The US and Cuba were not on speaking terms for more than 50 years following the 1959 revolution led by Fidel Castro and Che Guevara that overthrew Western-backed dictator Fulgencio Batista.

They installed a communist government and nationalised private businesses, including ones owned and operated by U.S. citizens. 

President Dwight D. Eisenhower responded with an embargo and cut off ties with the country a year later.

On April 17, 1961, President John F. Kennedy authorised a failed attempt to overthrow Castro, known as the Bay of Pigs invasion. The next year his administration expanded the embargo against Cuba to cover all areas of the economy.

Eight months later Cuba allowed the Soviets to build a missile base on the island as part of a secret accord, leading to the Cuban Missile Crisis and near nuclear war.

The 13-day stand-off involved U.S. naval ships surrounding the country until the US and the USSR came to an arrangement. The Soviets backed out of Cuba, America abandoned missile bases in Turkey and Italy.

Further sticking it to the Castro regime, President Lyndon B. Johnson in 1966 approved the Cuban Adjustment Act, which allowed citizens of the authoritarian country to apply for citizenship in the US if they could escape. 

The legislation was amended years later to say they must reach dry land in the US to stay.

In 1976 Cuban airliner Flight 455 was blown up off the coast of Barbados, with the death of 73 people. A CIA agent was allegedly involved.

In 1980 Fidel Castro allowed 125,000 Cubans to leave the island for the US in the so-called 'Mariel boatlift' (above). Many of those who went were criminals who were not wanted on the island, like the fictional Tony Montana character played by Al Pacino in Scarface.

In 1996 President Bill Clinton signed legislation specifying the embargo on the country could only be lifted when Fidel and his brother Raul were removed from power, and free and fair elections were held. 

Free speech must also be honored and dissidents must be released for the embargo to be removed. 

In 2006 Fidel temporarily handed over power to his brother Raul due to illness. His retirement became permanent in 2008.

Three years later, during his first term in office, President Obama began lifting restrictions on travel and remittances to the country. 

The two countries resumed diplomatic relations at Obama's urging on Dec. 14, 2015.

Prior to that U.S. and Cuban officials met in secret at the Vatican just outside Rome, Italy, to discuss the terms of reengagement.

Critics of the move say the U.S. got almost nothing in return for the deal. Arrests of Castro's political opponents have risen and Cuba has not made the kids of economic reforms the U.S. is seeking.

In return for Cuba's cooperation, 53 political prisoners, including jailed USAID worker Alan Gross, who had been convicted of espionage charges, were released. 

The United States likewise returned three captured Cuban intelligence operatives in the prisoner swap who were part of the Cuban Five, a group that was arrested for spying on the U.S. in 2001.

Cuba was later removed from the State Department's terrorist watch list in May of 2015.

The Obama administration believes the decades-old trade and travel ban on Cuba is fueling oppression in the island nation and wants Congress to throw it out. 

Tourism to Cuba is banned but the executive branch has unilaterally relaxed many travel rules and Americans can now go there for educational purposes on their own using the honor code as of last week.

Soon commercial flights to Cuba from the United States will also be available, as well.

Congress says it will not lift the full embargo on Cuba until the conditions set during Bill Clinton's administration are met