Charles and Camilla as well as William, Kate, George, Charlotte and Louis have an up-close view from the Buckingham Palace balcony of a military flypast.

Aircraft from the Royal Navy, British Army and Royal Air Force are flying over The Mall in central London.

The flypast was shortened from the planned six minutes to just over two minutes in length due to rainy weather in London Saturday.

Sources told ABC News royal contributor Omid Scobie that Prince Harry, Duke of Sussex, will be heading back to the United States soon after attending his father's coronation in London on Saturday.

"I'm here on the Duke of York steps, we've just seen the procession go back to Buckingham Palace and for Prince Harry, the Duke of Sussex, that probably brings his very quick trip to London to an end," Scobie said. "We saw him arrive on Friday evening getting ready, of course, for the big day to support his father at the coronation ceremony."

"But, of course, he also has duties back in Montecito, California, and sources close to the duke say that it is going to be an in-and-out trip for him," he added. "Just here to be part of that moment in Westminster Abbey, support his father and then be back at home to support his own family in Montecito."

The newly-crowned king and queen received a royal salute upon their return to Buckingham Palace.

Members of the military gave three cheers and played the national anthem as Charles and Camilla, wearing their crowns and robes, looked on.

As the new king and queen passed by in a golden carriage, hundreds of anti-monarchy protesters booed loudly in Trafalgar Square.

They also yelled chants of "what a waste of money" and "not my king."

-ABC News' Patrick Reevell

Prince Louis, the youngest child of Prince William and Kate, stole the show once again at his grandfather's coronation.

Louis, 5, joined his parents and siblings, Prince George, 9, and Princess Charlotte, 8, and other royal family members of the balcony of Buckingham Palace following the coronation service.

The youngster went viral on social media with his funny antics as he watched a military flypast zoom overhead.

Earlier, inside Westminster Abbey, Louis was seen alternatively yawning and looking around inquisitively as the pomp and circumstance of the coronation service played out before him.

Following the service, Louis joined his family inside a carriage in the procession back to Buckingham Palace.

Sitting by a window, Louis was seen waving and looking out at the crowds gathered to watch his family's historic day.