Meghan is believed to get on well with The Queen after accompanying Her Majesty on a series of engagements in Cheshire in June, where they were pictured laughing and smiling together.
Watched by the Queen and senior members of the royal family from the balcony of Buckingham Palace, the spectacle drew awe and applause from the crowd below.
Earlier today, the Duchess of Sussex and Duchess of Cambridge attended a special service at Westminster Abbey to mark 100 years of the Royal Air Force.
For her trip overseas, Meghan changed up her hairstyle with a side bun.
The queen stood out in an RAF-blue coat and dress edged with turquoise, with a matching hat and a diamond star brooch on her shoulder.
"Presenting the Royal Air Force with a new Queen's colour provides an opportunity to congratulate the service for your remarkable contribution to defence over the last 100 years", the Queen said.
The couple met RAF servicemen and women, charity representatives involved in the RAF100 Appeal, RAF Veterans and Civil Service personnel involved in the Centenary celebrations.
Meghan gave a nod to their host country upon arrival, wearing an emerald green dress by Givenchy, her wedding dress designer, as she and Harry, dressed in a suit, departed the plane.
Meghan Markle visited Dublin, Ireland, on Tuesday wearing the colors of the Irish flag.
The occasion concluded with 22 Typhoons spelling out "100" as they flew over Buckingham Palace, and then the Red Arrows flew over London.
The RAF, which is the first-ever independent air force, split from the British Army and Royal Navy in April 1918.
Harry and Meghan later joined royals at a Buckingham Palace reception to mark the centenary of the Royal Air Force.