Queen Elizabeth II doesn't want Prince William to fly a chopper with his entire family on board, and there is reportedly a personal reason that she is so worried about such trips.

A source close to her had told The Sun earlier this month that the monarch 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 Duke of Cambridge, who served as a full-time pilot with the East Anglian Air Ambulance from July 2015 for two years, regularly flies between his London residence, Kensington Palace, and Norfolk country home, Anmer Hall, with his wife Kate Middleton and their three children Prince George, Princess Charlotte, and Prince Louis.

As per a new report in Mail Online, the 95-year-old is extra concerned about William's choice of transport with his family because she is still haunted by a helicopter accident that killed Air Commodore John Blount, the Captain of the Queen's Flight, and three others. The tragedy happened in December 1967 when the Captain was flying in a Westland Whirlwind that crashed near Newbury, Berkshire. An inquest into the matter blamed metal fatigue in the gearbox.

No member of the royal family was onboard the helicopter at the time of the accident. However, the Queen's husband Prince Philip had recently been flying the same aircraft, which left her so upset that she refused to contemplate rotary air travel altogether.

She did not set foot in a helicopter for a long time after that, until she had no choice but to travel in one during her Silver Jubilee celebrations in 1977. She wanted to visit Northern Ireland, but her ministers told her that the only safe way to travel there would be in a chopper.

However, she still shies away from travelling in them, especially in winters, and never boards one after dark. A source close to the monarch told Richard Eden, "It put her off completely. That's why she is so worried about William and his family."

The source added that the monarch is planning to discuss her concerns with her grandson again when he returns from his Norfolk home where he is spending the Christmas holidays with Kate and their three children.

Queen Elizabeth II
Queen Elizabeth II attended last year's ceremony at the Cenotaph, which commemorates military veterans and the fallen in all conflicts since World War I the First World War and services across Commonwealth countries remember servicemen and women who have fallen in the line of duty since WWI. Photo: POOL via AFP / Aaron Chown