The Queen and senior Royal Family members will view a fly-past from the balcony of Buckingham Palace today, on the 75th anniversary of the start of the Battle of Britain.
The monarch will join the Duke of Edinburgh, the Duke of Cambridge and the Duke of York to witness the fly-past by four Spitfires, two Hurricanes and four Typhoons during an enhanced Changing the Guard.
The spectacle is being held to mark the 75th anniversary of the start of the Battle of Britain - one of the Second World War's pivotal conflicts which halted German invasion plans.
During the summer and autumn of 1940, 544 personnel from Fighter Command died as the RAF fought in the skies above southern England to force back the threat of any invasion by Hitler.
July 10 1940 is widely acknowledged to be the start of the battle, with a series of Luftwaffe attacks on shipping convoys off the south-east coast of England.
The 75th anniversary is likely to be the last major anniversary at which the remaining members of wartime prime minister Winston Churchill's famous "Few" will be fit to take part.
Today's enhanced guard change will be performed by the RAF Queen's Colour Squadron, in front of guests including six surviving RAF Battle of Britain pilots.
Later, the airmen will have a reception and lunch at the RAF Club in Piccadilly attended by royals including Philip, William, and the Earl and Countess of Wessex.
On Sunday, a memorial day will be held at the National Memorial to the Few at Capel le Ferne on the famous white cliffs between Dover and Folkestone in Kent.
Prince Michael of Kent, the Battle of Britain Memorial Trust's patron, will take the royal salute during a day which will feature a display by the Battle of Britain Memorial Flight.
The day, which will be attended by eight veterans who are all well into their 90s, will end with a sunset ceremony.
Trust chairman Richard Hunting said: "Memorial Day is the most important date in our calendar and we are looking forward to again welcoming a number of the Few.
"It is a privilege to have such men amongst us and we know that their presence will make the 75th anniversary of what was arguably the most important battle fought by this country in the whole of the last century a very special day."