After the royal appearance, the family watched the flypast from a balcony at Buckingham Palace with great ceremony.
Duchess Kate was attending the celebration a day after she appeared at the Chapel Royal in St. James's Palace for the christening of her third baby, Prince Louis of Cambridge, who was born April 23.
And amid turmoil in the Cabinet and her Government, Mrs May delivered a reading at the service, Hebrews 11:32-12:2, with the head of the RAF Air Chief Marshal Sir Stephen Hillier also taking to the lectern.
Anyone meeting Meghan Markle for the first time might easily be star-struck - a well-known actress turned duchess isn't someone you come across very often.
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The duchess of Cambridge, who has put in brackets her maternity leave for this major sporting event, will be back at Wimbledon on Sunday, July 15, alongside prince William to attend the final gentlemen.
She attended her brother-in-law's wedding in May, Trooping the Colour in June, and now the RAF centenary commemorations. To release, Middleton chose a stylish dress from your favorite British brand Alexander McQueen. She was photographed wearing a RAF Dacre brooch on her lapel and a matching blue hat.
Meghan, Duchess of Sussex, wore a striped shirt and white pants, while Kate, Duchess of Cambridge, sported a polka dot dress.
For both Prince Louis and Princess Charlotte's christenings, Kate opted to accompany the look with a low bun, however for Prince George's she wore her hair loose. Kate Middleton went with an icy blue dress by her go-to designer, Alexander McQueen, and a hat by Sean Barrett.
According to Harper's Bazaar, Kate wore a white dress with puff sleeves and a midi-length hemline.