A diplomatic gaffe happened during King Charles and Queen Camilla's visit to Arlington National Cemetery during their state visit to the U.S.

After saying farewell to President Donald Trump and first lady Melania Trump on April 30, the King, 77, and Queen, 78, visited the military cemetery in Arlington, Virginia, to pay their respects at one of the United States' most significant sites of military remembrance.

There, the royals laid a wreath and posy at the Tomb of the Unknown Soldier to honor the fallen and the military partnership between the United Kingdom and the United States, but a problem was spotted with the Union Jack flag on parade there.

The national flag of the U.K. featured in the King and Queen's escort was flown upside down.

Britain's Flag Institute explains that there is a correct way to raise the national emblem. To fly the Union Jack in the proper position, "in the half of the flag nearest the flagpole, the wider diagonal white stripe must be above the red diagonal stripe, as Scotland's St. Andrew's Cross takes precedence over Ireland's St. Patrick's Cross.".....

The flag mishap was the second such snafu to make waves during King Charles and Queen Camilla's state visit to the U.S. this week to commemorate America's 250th anniversary of independence.

On April 24, the Friday before the trip kicked off, ABC News reporter James Longman said that Australian flags were briefly raised alongside American flags on the light posts lining a major thoroughfare of Washington, D.C., the King and Queen's first major stop stateside.

"For about two hours, they put the Australian flag up alongside the Stars and Stripes… I think they realized their mistake, and they've replaced them now with the Union Jack," Longman said in a video shared to Instagram.