It was 100 years ago, on April 1 1918, that the Royal Flying Corps and the Royal Naval Air Service merged to create the RAF - the world's first independent air service.
But while arriving at the Royal Air Force Westminster Abbey service on Tuesday, the Duke and Duchess opted for a close but coy gesture of affection in public, with Meghan holding tightly onto her husband's arm during their arrival.
Photos from the christening of Prince Louis showed that if anyone was nervous before the ceremony in the chapel Royal St. James's Palace, it is not exactly the main character of the day.
With an RAF ensign draped over the high altar behind him in the abbey, Mr Welby also highlighted how members of his own family have served and been killed in the RAF - drawing attention to his own father who flew low level sorties in Burma. She also wore the diamond and ruby RAF Dacre brooch, which was given to her in 2015.
Kate wore an icy blue Alexander McQueen coat dress and a matching hat from Sean Barrett.
Previously, it had been awarded to the top female cadet each year, but in 2015 the tradition was altered to give female cadets the same prize as male cadets, and the brooch was given to Kate.
Ahead of the speech, the Queen presented a new flag, known as a "Colour" to the RAF Regiment.
She later added: "I hope he stays like this".
She further remembered her father George VI, who became the first member of the Royal Family to qualify as a Royal Air Force pilot.
WPA Pool via Getty Images The royals observe the RAF 100th anniversary flypast from the balcony of Buckingham Palace on July 10 in London. We'll, of course, let you know if they do.