LONDON (CNN) -- Queen Elizabeth attended an event celebrating 100 years of Britain's Royal Air Force (RAF) on Tuesday that included a huge flypast of around 100 aircraft.
Her appearance came one day after the monarch, 92, and her husband, Prince Philip, 97, missed the christening of their sixth great-grandchild, Prince Louis. Both have been scaling back their public and private engagements in recent years.
The UK's Press Association said the decision to miss the christening was understood not to have been made for health reasons and was mutually agreed to by the Queen and Louis' parents, the Duke and Duchess of Cambridge, some time ago.
The Queen attended the event in central London on Tuesday with her son and heir to the throne, the Prince of Wales and his wife the Duchess of Cornwall, Prince William and Catherine and Prince Harry and his wife Meghan. Prince Philip did not attend.
Speaking at the event, the Queen congratulated the RAF for its "remarkable contribution to defense over the last hundred years."
"Tenacity, skill and gallantry have been your hallmarks as you have helped to safeguard freedom and security in many parts of the world," she said. "The RAF has won a place in the heart of our nation."
First on the agenda was a service in Westminster Abbey celebrating 100 years of the RAF, which came into formal existence on April 1, 1918, just a few months before the end of World War I.
Hundreds of servicemen and women then took part in a parade on the Mall, leading up to Buckingham Palace, before members of the royal family gathered to watch the flypast, which included Chinooks, Spitfires, Hawks and Red Arrows.
The flypast was followed by a solemn rendition of the national anthem, "God Save the Queen," as members of the military formed themselves into the phrase "RAF 100" on the terrace below the palace balcony.
Some roads in central London were closed ahead of the parade and flypast, Transport for London announced Tuesday.
The royal family has a long history with the Royal Air Force. In her speech, the Queen described how her father, King George VI, became the first member of her family to qualify as an RAF pilot in 1918.
"The Duke of Edinburgh, the Prince of Wales and the Duke of Cambridge have all earned their wings and wear them with great pride," she said.
Prince William -- the Duke of Cambridge -- is the most recent member of the family to qualify, receiving his RAF pilot's wings in 2008 and later qualifying as an operational captain with the RAF Search and Rescue Force. He left active service in 2013.
The celebrations Tuesday marked the second event in a busy week for Britain's royals, following Monday's christening and ahead of the Queen's meeting with US President Donald Trump at Windsor Castle on Friday.
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