The queen, 96, and Louis, 4, watched military planes fly above the palace as the festivities for the queen's Platinum Jubilee unfolded in the center of London.
Louis appeared to ask his great-grandmother questions about the planes overhead, while the queen was seen pointing things out to her great-grandson.
Queen Elizabeth II, Kate, Duchess of Cambridge, Prince Louis, Princess Charlotte watch from the balcony of Buckingham Place after the Trooping the Color ceremony in London, June 2, 2022.
Aaron Chown/AP
Camilla, Duchess of Cornwall, Prince Charles, Prince of Wales, Queen Elizabeth II, Prince Louis of Cambridge, Catherine, Duchess of Cambridge, Princess Charlotte of Cambridge, Prince George of Cambridge and Prince William, Duke of Cambridge on the balcony of Buckingham Palace watch the RAF flypast during the Trooping the Colour parade on June 2, 2022 in London.
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Louis' older brother and sister, Prince George, 8, and Princess Charlotte, 7, were also on the balcony, along with other members of the royal family, including the siblings' parents, Prince William and Duchess Kate.
The Royal family watches the RAF flypast on the balcony of Buckingham Palace during the Trooping the Color parade on June 2, 2022 in London.
Chris Jackson/Getty Images
William provided fashion inspiration for Louis, who wore a sailor-inspired white and blue outfit that appears to be the same one William wore at Trooping the Color in 1985.
Prince William watches the scene of Trooping the Colour from the balcony of Buckingham Palace on June 15, 1985 in London; Britain's Prince Louis of Cambridge holds his ears as he stands next to Britain's Queen Elizabeth II to watch a special flypast from Buckingham Palace balcony following the Queen's Birthday Parade, the Trooping the Colour, as part of Queen Elizabeth II's platinum jubilee celebrations, in London on June 2, 2022.
PA Images via Getty Images, FILE|Chris Jackson/Getty Images
This year's Trooping the Color is only the second one Louis has attended.
He made his debut in 2019, as a toddler, and then for the next two years only a modified Trooping the Color was celebrated due to the coronavirus pandemic.
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Prince Louis makes his Trooping the Colour debut
Duchess Meghan also made her first public appearance during the Queen's birthday celebration since introducing baby Archie to the world.
ABCNews.com
This year, Louis got to ride in a horse-drawn carriage to Buckingham Palace alongside George, Charlotte, Kate and Camilla, Duchess of Cornwall.
Prince George of Cambridge, Prince Louis of Cambridge and Princess Charlotte of Cambridge travel in a horse-drawn carriage during the Queen's Birthday Parade, the Trooping the Color, as part of Queen Elizabeth II's platinum jubilee celebrations, in London, June 2, 2022.
Aaron Chown/POOL/AFP via Getty Images
Once the family arrived at Buckingham Palace, Louis was seen peering out of a window before he and his family joined the queen on the balcony.
Prince George, Princess Charlotte and Prince Louis watch the Trooping of the Color in London, June 2, 2022.
Matt Dunham/AP
Catherine, Duchess of Cambridge, Prince George, Princess Charlotte and Prince Louis during Trooping The Color, June 2, 2022 in London.
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Throughout the day, Louis appeared both bored and excited to be at Trooping the Color, a royal tradition that takes place each year on the reigning monarch’s official birthday.
Take a look at some of his best reactions.
Catherine, Duchess of Cambridge talks to Prince Louis who is pulling a funny face, as they stand with Princess Charlotte of Cambridge to watch a special flypast from Buckingham Palace balcony in London on June 2, 2022.
Daniel Leal/AFP via Getty Images
Queen Elizabeth II, Prince Louis, Kate, Duchess of Cambridge, and Princess Charlotte on the balcony of Buckingham Palace, London, June 2, 2022.
Alastair Grant/Pool Photo via AP
Britain's Prince Louis of Cambridge holds his ears as he stands next to Britain's Queen Elizabeth II to watch a special flypast from Buckingham Palace balcony following the Queen's Birthday Parade, the Trooping the Colour, as part of Queen Elizabeth II's platinum jubilee celebrations, in London on June 2, 2022.
Daniel Leal/AFP via Getty Images
Britain's Prince Louis, Princess Charlotte and Prince George react as they watch a special flypast from Buckingham Palace balcony following the Queen's Birthday Parade, the Trooping the Color, as part of Queen Elizabeth II's platinum jubilee celebrations, in London, June 2, 2022.
Daniel Leal/AFP via Getty Images
Queen Elizabeth, Prince Charles and Catherine, Duchess of Cambridge, along with Princess Charlotte and Prince Louis appear on the balcony of Buckingham Palace as part of Trooping the Color parade during the Queen's Platinum Jubilee celebrations in London, June 2, 2022.
Hannah Mckay/Reuters
Prince George, Prince Louis and Princess Charlotte ride in a carriage as they attend the celebration of Britain's Queen Elizabeth's Platinum Jubilee, in London, June 2, 2022.
Peter Nicholls/Reuters
Prince Louis, Catherine, Duchess of Cambridge, Princess Charlotte, Prince George and Prince Willia watch the RAF flypast on the balcony of Buckingham Palace during the Trooping the Color parade on June 2, 2022 in London.
Chris Jackson/Getty Images
Catherine, Duchess of Cambridge, (2R) reacts as Britain's Prince Louis of Cambridge (2L) covers his ears, as they stand with Queen Elizabeth II (L), and Princess Charlotte of Cambridge to watch a special flypast from Buckingham Palace balcony following the Queen's Birthday Parade, the Trooping the Colour, as part of Queen Elizabeth II's platinum jubilee celebrations, in London, June 2, 2022.
Daniel Leal/AFP via Getty Images
Prince Louis of Cambridge reacts as he watches a special flypast from Buckingham Palace balcony following the Queen's Birthday Parade, the Trooping the Color, as part of Queen Elizabeth II's platinum jubilee celebrations, in London, June 2, 2022.
