King Charles’s former pilot, Graham Laurie, explained to OK! Magazine:

“We flew all four: the Prince, the Princess, Prince William, and Prince Harry, up until Prince William was 12 years old. After that, he had to have a separate aircraft, and we could only fly all four together when they were young with written permission from Her Majesty. When William became 12, he would fly normally in a 125 from Northolt, and we would fly the 146 out with the other three on.”

Though not an official law, this unwritten rule has been followed for decades and is based on more than just superstition. Several royal family members have tragically died in air accidents, reinforcing the need for caution. Prince Philip’s sister, Princess Cecilie, died in a plane crash in 1937. In 1942, Queen Elizabeth II’s uncle, Prince George, was killed in a similar accident, and her cousin, Prince William of Gloucester, also lost his life in a plane crash in 1972.

That said, the travel rule is ultimately at the monarch’s discretion, meaning King Charles or Prince William could choose to modify or waive it.

Prince William himself has previously been granted an exception. In 2014, he and Kate received special permission to travel together with their three children during their Australian tour, prioritizing convenience over tradition.

At the time, the royal press office confirmed to BBC Newsround:

“They had to ask the Queen for permission, but she said yes. While there is no official rule on this, and royal heirs have traveled together in the past, it is something that the Queen has the final say on.”

Whether Prince George’s upcoming travel restrictions will remain in place or be adjusted remains to be seen, but as history has shown, royal tradition plays a significant role in shaping the path to the throne.