The Red Arrows perform a fly past over the Queen Victoria Memorial and Buckingham Palace to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Henry Nicholls 

Britain's Queen Elizabeth and Meghan, Duchess of Sussex stand on the balcony of Buckingham Palace as they watch a fly past to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Chris Radburn 

The Red Arrows perform a fly past over Trafalgar Square to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Hannah McKay 

Britain's Prince Charles, Camilla, Duchess of Cornwall, Queen Elizabeth, Meghan, Duchess of Sussex, Prince Harry, Prince William, Catherine, Duchess of Cambridge and Princess Anne stand on the balcony of Buckingham Palace as they watch a fly past to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Chris Radburn 

Military aircraft perform a fly past over Trafalgar Square to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Hannah McKay 

Britain's Meghan, Duchess of Sussex, Prince Harry, Prince William, Catherine, Duchess of Cambridge stand on the balcony of Buckingham Palace as they watch a fly past to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Chris Radburn 

The Red Arrows perform a fly past over the Mall and Buckingham Palace to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Henry Nicholls 

Vintage military aircraft perform a fly past over the Queen Victoria Memorial and Buckingham Palace to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Henry Nicholls 

Typhoon jets take part in a flypast over the financial district to mark the centenary of the Royal Air Force (RAF) in London, Britain, July 10, 2018. REUTERS/Kevin Coombs 

The Red Arrows perform a fly past over the Mall and Buckingham Palace to mark the centenary of the Royal Air Force in central London, Britain July 10, 2018. REUTERS/Henry Nicholls