The president and first lady are expected to land just before 5 p.m. local time (12 p.m. EDT) Wednesday in Shannon, where Trump is scheduled to meet with Prime Minister Leo Varadkar.
Update 6:52 a.m. EDT June 5: During the D-Day anniversary ceremony, Trump took the stage to read from former President Franklin Delano Roosevelt's "Mighty Endeavor" prayer.
Update 6:26 a.m. EDT June 5: Trump, Queen Elizabeth II and other world leaders will mark D-Day's 75th anniversary Wednesday at a ceremony in Portsmouth, England.
Earlier Wednesday, Trump tweeted that he "could not have been treated more warmly in the United Kingdom by the Royal Family or the people."
He added: "Our relationship has never been better, and I see a very big Trade Deal down the road."
The tweet came amid reports of mass protests in London during Trump’s three-day visit.
Update 2:10 p.m. EDT June 4: Trump and Brexit Party leader Nigel Farage met Tuesday at the U.S. ambassador's residence in London on the second day of the president's three-day trip to the U.K.
In a tweet posted after the meeting, Farage said Trump “really believes in Brexit and is loving his trip to London.”
Farage has campaigned for years to take Britain out of the European Union and is one of Trump’s most prominent British supporters. The president has called Farage a friend.
Update 10 a.m. EDT June 4: Trump and British Prime Minister Theresa May spoke Tuesday at a joint news conference in London.
May, who is set to step down Friday as leader of her Conservative Party, praised the “precious and profound” U.S.-U.K. special relationship but acknowledged differences with Trump on issues including climate change and Iran.
Trump reiterated his commitment to reaching a “phenomenal” trade deal with Britain, though it will be up to the United Kingdom’s next prime minister to achieve any bilateral trade deal with the U.S.
Trump also decried reports of mass protests in London as “fake news,” saying he has seen only a “small protest” since arriving in the U.K.
Photos and video from London showed thousands of people gathered in London to protest Trump on Tuesday.
Update 8:30 a.m. EDT June 4: Trump and British Prime Minister Theresa May are scheduled to speak Tuesday at a joint news conference in London.
The president and first lady Melania Trump met earlier with the prime minister, who is set to step down Friday as head of her Conservative Party over her failure to secure Britain’s exit from the European Union.
Trump praised May at a business round table at St. Jame's Palace and predicted a "very substantial trade deal" between the U.S. and the U.K., The New York Times reported.
Speaking to May at the meeting, the president said, “I don’t know exactly what your timing is, but stick around, let’s do this deal.”
The leaders discussed a possible bilateral trade deal to take effect once the U.K. leaves the European Union and Britain's decision about whether Chinese telecoms firm Huawei can work on parts of the country's new 5G wireless communications network. The U.S. wants allies to exclude Huawei from all 5G networks over fears it could let the Chinese government gain access to data.
Update 7:50 p.m. EDT June 3: Queen Elizabeth II rolled out the red carpet for President Trump and his family at a state banquet Monday night at Buckingham Palace.
President Donald Trump appeared to appreciate the pomp and circumstance of the British royals during his meetings with them on Monday and at the official state banquet.
During a speech and toast before the elaborate dinner, the queen had kind words for the United States and said the alliance between the two nations has insured the "safety and prosperity of both our peoples for decades.”
She praised the post-World War II international institutions, like NATO and the United Nations, that were created to insure "the horrors of conflict would never be repeated".
Trump, in his toast, praised the courage and strength of the British people during World War II and called the queen a “great, great woman.”
“In that dark hour, the people of this nation showed the world what it means to be British,” Trump said.
Update 3:55 p.m. EDT June 3: All four of Trump's adult children were present Monday for a state banquet with Queen Elizabeth II at Buckingham Palace.
The royal family share a sneak peak of their preparations for the affair earlier Monday.
Including the queen, 171 people are participating in Monday’s state banquet, according to pool reports.
Update 3 p.m. EDT June 3: Trump said in a tweet Monday that the "London part of (the) trip is going really well."
“The Queen and the entire Royal family have been fantastic,” Trump wrote. “The relationship with the united Kingdom is very strong.”
He said he had not seen protests in the city, though The Associated Press noted the president has "largely been getting around by helicopter."
Trump did not mention his ongoing fued with London Mayor Sadiq Khan, who the president called “a stone cold loser” early Monday.
He also made no mention of his calling Prince Harry’s wife, who was formerly known as Meghan Markle, “nasty”
Update 11:30 a.m. EDT June 3: Trump and first lady Melania Trump have arrived at Clarence House, where they will have afternoon tea in a private meeting with Price Charles and his wife, Camilla.
Update 10:20 a.m. EDT June 3: Trump laid a wreath Monday at the Tomb of the Unknown Warrior at Westminster Abbey after meeting with Queen Elizabeth II at Buckingham Palace.
Earlier Monday, the queen gave Trump and first lady Melania Trump a look at items in the Royal Collection, one of the largest collections of art and other objects in the world.
Update 7:16 a.m. EDT June 3: President Donald Trump and first lady Melania Trump have arrived at Buckingham Palace, where they were greeted by Britain's Prince Charles and his wife, Camilla, Duchess of Cornwall.
Trump then shook hands with Queen Elizabeth II.
Original report: According to BBC News, Air Force One touched down shortly before 9 a.m. local time (4 a.m. EDT) at London Stansted Airport.
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The trip marks Trump's first official state visit to the U.K. Although he met with Queen Elizabeth II last summer, that trip was considered a "working visit," CNN reported. In contrast, state visits usually feature "royal pomp," according to The Associated Press.
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Trump and his wife, first lady Melania Trump, are expected to have lunch with the queen Monday, CBS News reported. The agenda also includes "a grand welcoming ceremony at Buckingham Palace"; tea with Prince Charles and his wife, Camilla, Duchess of Cornwall; and a state banquet, The Associated Press reported.
Although Prince William and his wife, Catherine, Duchess of Cambridge, are expected to attend Monday's banquet, Prince Harry's wife, Meghan, Duchess of Sussex, is not, the BBC reported. The new mom just gave birth to a son, Archie, last month and is on maternity leave.
During his visit, Trump also is scheduled to attend "D-Day commemoration ceremonies on both sides of the English Channel," the AP reported.
Trump's visit already is causing controversy in Britain. Minutes before he landed in London, Trump slammed London Mayor Sadiq Khan on Twitter, calling him "a stone cold loser."
Trump also made headlines last week over remarks he made to the Sun, a British tabloid, about the Duchess of Sussex, formerly known as Meghan Markle. After a reporter told Trump that Markle had criticized him in the past, Trump replied: "I didn't know that she was nasty," the outlet reported.
Trump denied making the comment, even though the Sun posted audio of the interview.
The Associated Press contributed to this report.