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

As Charles was crowned king, ABC News royal contributors weighed in on the moment.

Robert Jobson said he was feeling "deep pride in my country and the royal family and the clergy."

"Particularly a bit of relief for the king because I thought when the archbishop was trying to get that crown on his head, he was trying a little too hard," Jobson added, with a laugh.

Victoria Murphy commented on how the "mood really shifted."

"It was very solemn, it was quite tense, it felt very serious and then suddenly, it actually feels quite joyous now," Murphy said. "It feels like a moment of celebration."

Sir Peter Westmacott, who previously served as Charles' secretary, said he also felt "a sense of great pride" and is "delighted for my old boss."

"It's a wonderful moment of pageantry and the mixture of humility and service," Westmacott added, "but also the crowning of a monarch in a way that no other country in this world still does or indeed knows how to do as we do."

Ailsa Anderson, who previously served as press secretary to Charles' late mother, Queen Elizabeth II, described feeling "rather emotional about it all."

"However you prepare for something like this, to actually see it has made me swell with pride but also emotional and also proud of my former boss, the Archbishop of Canterbury, who has been faultless in this service," Anderson said. "I think this service is pretty stupendous."

Kristina Kyriacou, who previously served as the communications secretary to Charles and Camilla, said she was "absolutely overjoyed."

"I couldn't be happier. I feel very, very emotional," she added. "This is a king who has worked every second and every hour of the day for the past 60 years. You know, since his teens, he has absolutely worked in public service serving his mother, serving the nation and the commonwealth -- and he deserves this. And I hope everyone understands all the good that he has done and all the causes that he has championed."