A flypast involving about 40 Spitfires and Hurricanes is set to take place over London to commemorate the 75th anniversary of the Battle of Britain.
Prince Harry will join veterans to see the fleet of Battle of Britain aircraft take to the air - the most in any one place since World War II.
A service will also be held at London's St Paul's Cathedral at 11am local time.
The Battle of Britain, in the summer of 1940, was one of the pivotal moments in British history.
A range of events has already been staged over the past few months to mark the aerial battle, which raged between July and October 1940 as Germany attempted to destroy the fighting capacity of the RAF.
Tuesday's flypast and service are being held on Battle of Britain Day - the name given to the day, on 15 September 1940, when the German Luftwaffe launched its largest and most concentrated attack against London in the hope of drawing out the Royal Air Force.
Spitfires, Hurricanes and Blenheims, from across Britain, the United States and Europe will come together at Goodwood Aerodrome, West Sussex, to take part in the flypast. Present-day owners, operators, pilots and engineers will be there alongside veterans.
Battle of Britain pilot Wing Commander Tom Neil, now 95, will lead the formation from the rear seat of a two-seat Spitfire.
He will be joined by wounded service personnel who have been training to fly the Spitfire as part of the Spitfire Scholarship set up by the Boultbee Flight Academy in partnership with the Royal Foundation's Endeavour Fund, which Prince Harry launched at Goodwood in 2014.
The aircraft will take off in groups from midday and fly over Goodwood before dispersing around the South of England.
Some will return to Goodwood, while others will end up at Battle of Britain airfields including Biggin Hill and Northolt.