The King wore a black armband in tribute to those killed in the Air India plane crash as the Trooping the Colour ceremony staged in his honour took place.
Military pomp and pageantry were on display to mark the milestone, but the event also remembers those killed in the devastating crash, which claimed the lives of 241 passengers and crew, including more than 50 British nationals, as well as around 30 people on the ground.
The King requested a minute’s silence be observed in tribute to the passengers and crew killed, and others affected, when the Boeing 787 Dreamliner bound for Gatwick Airport came down on Thursday in the Indian city of Ahmedabad.
Black armbands are being worn by the head of state and senior royals riding in the ceremony, also known as the King’s Birthday Parade, staged in Horse Guards Parade in Whitehall.
The event marks Charles’ official birthday, and the appearance of the Prince and Princess of Wales’ children sparked cheering when they were spotted in a carriage with their mother, Kate.
Prince George, Princess Charlotte and Prince Louis were all beaming in the sunshine as they left Buckingham Palace in a coach ahead of the Trooping the Colour ceremony, following the King and Queen.
Royal fans were delighted to spot seven-year-old Louis, loved for his mischievous behaviour at royal events, who grinned and appeared to wave to onlookers.
George, Charlotte and Louis then joined other members of the monarchy in the former office of the Duke of Wellington to watch the Trooping the Colour spectacle in honour of their grandfather, the King.
Other coaches were spotted carrying the Duchess of Edinburgh, Vice Admiral Sir Tim Laurence, and the Duke and Duchess of Gloucester.
Riding behind the King were the royal colonels wearing black armbands – the Prince of Wales, who is Colonel of the Welsh Guards; the Princess Royal, Colonel of the Blues and Royals; and the Duke of Edinburgh as Colonel of the Scots Guards.
The Royal family then later gathered on the balcony at Buckingham Palace to watch the Red Arrows fly down the Mall.
The world-famous aerobatic display team made history when they used sustainable fuel and vegetable oil for their flypast.
Jets were powered by a blend of sustainable aviation fuel, and used the vegetable oil to produce their trademark vapour trails.
A Buckingham Palace spokesperson said the King requested amendments to the Trooping the Colour programme “as a mark of respect for the lives lost, the families in mourning and all the communities affected by this awful tragedy”.
A minute’s silence was observed after the King inspected the guardsmen on the parade ground.
In 2017, Trooping was held a few days after the Grenfell Tower blaze and the loss of life was marked by a minute’s silence, a decision taken by Queen Elizabeth II.
The King issued a written message soon after the Air India plane crash saying he was “desperately shocked by the terrible events” and expressing his “deepest possible sympathy”.
He was kept updated about the developing situation on Thursday and it later emerged there was a sole survivor, UK national Vishwash Kumar Ramesh.
Trooping the Colour will see more than 1,000 servicemen taking part in the military display who when not performing ceremonial duties are fighting soldiers.
The colour - regimental flag - being trooped this year is the King’s Colour of Number 7 Company, Coldstream Guards, a prestigious regiment known as the sovereign’s bodyguard which is celebrating its 375th anniversary this year.
The day will end with the royal family gathering on Buckingham Palace’s balcony for the traditional RAF flypast.
