The Coronation flypast is at risk of being cancelled due to bad weather and contingencies are being put in place if cannot go ahead or it needs to be scaled down.
Members of the Royal Family are set to line up on the Buckingham Palace balcony to watch aircraft, including the Red Arrows, Typhoons, Apache helicopters and a Lancaster bomber, fly by at 2.30pm.
But the Met Office warned that showers are on the cards and clouds will be widespread on Saturday, which could potentially impact safety, meaning that the flypast may need to be modified or cancelled altogether.
The RAF will assess the weather forecast until the last minute and only make a decision about cancelling the flypast one or two hours before it is due to take place.
According to reports, parts the flypast or all of it could be moderated or cancelled outright due to the weather.
Met Office forecaster Simon Partridge told The Telegraph that rain is likely by Saturday lunchtime, which is "not ideal" but appears to be "tradition" as previous Coronations - including that of Queen Elizabeth II - also experienced rain.
Because of the Coronation, flight restrictions will be imposed on light aircraft and drones above London on Friday and Saturday.
Transport Secretary Mark Harper also banned aircraft from flying below 2,500ft in an area including Buckingham Palace and Westminster Abbey from 9am tomorrow until 9pm on Saturday.
Commercial flights will not be affected, it is understood.
That is in contrast with the day of the late Queen's funeral, when more than 100 Heathrow Airport flights were cancelled to prevent aircraft noise disturbing proceedings at Westminster Abbey and Windsor Castle.
At around 2.15pm on May 6, the King and Queen Consort will appear on the balcony of Buckingham Palace with other members of the Royal Family to watch a six-minute flypast of more than 60 aircraft from the Royal Navy, British Army and Royal Air Force over The Mall.
The aircraft will then fly into airspace above Surrey, Berkshire, Buckinghamshire, Oxfordshire, Gloucestershire and Wiltshire.
A document published by the Civil Aviation Authority and air traffic control service Nats setting out the exact details and locations of the rules states: "Due to the large number of aircraft involved (in the flypast), the Secretary of State for Transport has decided that it is necessary to introduce Restriction of Flying Regulations."
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Talking about Saturday's weather conditions, a Ministry of Defence spokesman said: "As is always the case for flypasts of this type, the latest weather information will be obtained, and weather checks will take place in advance of the main flypast on Saturday.
"Depending on the weather, there are a number of contingencies in place."
