Queen's grave fears for Prince William's helicopter flying: 'It keeps her up at night'

The Queen is "terrified" members of the royal family will be injured or killed while flying in helicopters and is urging Prince William to stop piloting the aircraft.

According to The Sun, Her Majesty has raised concerns with the Duke of Cambridge, 39, about flying with his wife Kate Middleton, 39, and three children Prince George, eight, Princess Charlotte, six, and three-year-old Prince Louis, amid fears the line of succession could be threatened.

A source close to the royals claims the Queen, 95, is "terrified" disaster could strike and has spoken to the future King about avoiding such air travel, particularly piloting helicopters himself.

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"Her Majesty has told close friends and courtiers that she would like William to stop flying himself, particularly in bad weather, as helicopters are not the safest form of transport," the source told The Sun.

"It keeps the Queen awake at night and she is understandably very worried."

The source added: "The Queen has told William she is worried that, however good he is as a pilot, bad weather and accidents can strike at any time.

"She thinks the future is bright with them at the helm after Charles but if something happened to him and the family it doesn't bear thinking about."

If something happens to Prince William, Prince Harry — who is no longer a working senior royal — will be bumped up in the line to the throne after Prince Charles.

Prince William is known to pilot helicopters when family members are on board, the publication states.

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There is an unwritten rule which prohibits senior royals from flying together in the event of a deadly incident, however protocol has been reportedly "relaxed" as Prince William and Kate had more children and split their time between London and Norfolk.

A Palace official said in 2014: "While there is no official rule on this, and royal heirs have travelled together in the past, it is something the Queen has the final say on."

The insider claims the Queen has had several private conversations with William about using helicopters.

The Duke of Cambridge has also been known to fly his family the 185km from Kensington Palace to their property in Anmer Hall, Norfolk.

The Cambridges recently released their annual Christmas card from a holiday in Jordan, and it is believed William and Kate travelled there together with their three children.