Prince George and Princess Charlotte goof off at palace window, stick out tongues

It could become a royal tradition:  While the grownups wave from the Buckingham Palace balcony, the royal kiddies gleefully peek through a palace window, tongues wagging.

It happened Tuesday when the two royal heirs, Prince George, 4, and Princess Charlotte, 3, had what looked like a delightful time at a window, waving and laughing during celebrations of the centenary of the Royal Air Force.

As their nanny, Maria Teresa Turrion Borrallo, and an aide to their mother, Duchess Kate of Cambridge, looked on, Charlotte pulled one of her signature looks: She stuck out her tongue.

George was a little more mature (he turns 5 on July 22) but his mouth was still open with excitement.

He was dressed in a dark shirt while Charlotte was in one of the patterned smock dresses her mother favors.

George is no stranger in the tongue-wagging department: He was spotted at the window during the Trooping the Colour ceremony in June 2015, mouth agape, tongue out, hands raised and laughing uproariously as his nanny grinned.

The occasion for all this giggling on Tuesday was an elaborate celebration of the RAF led by the children's great-grandmother, Queen Elizabeth II, and attended by their royal relations, including their parents, Prince William and Duchess Kate, and their uncle Prince Harry and his new wife, Duchess Meghan of Sussex.

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The day started with a service at Westminster Abbey, followed by a colorful parade of troops on The Mall, ceremonies in the palace forecourt in which the queen took the salute and presented the RAF with a new Queen's Colour, and then a spectacular fly-by of RAF planes.

The grownups flanked the queen on the palace balcony, waving at a huge crowd that stretched below them along on the Mall in front of Buckingham Palace. They looked upward as the RAF planes roared over the palace and central London.

Although both George and Charlotte (third and fourth in line to the throne, respectively) have appeared on the balcony this year with their parents, the RAF celebration was deemed an adults-only affair.

But they still managed to have fun.

The Cambridge children are not often on display in public but it was a second glimpse of them after Monday's christening ceremony for baby brother Prince Louis, who was born April 23, in the Chapel Royal of St. James's Palace in London.

WJAX