Prince William's first son, Prince George, recently turned 12, and according to reports, this has triggered a royal protocol requiring heirs to travel separately to protect the line of succession.

While not a formal rule, it is reportedly a long-standing tradition upheld since the reign of Queen Elizabeth II.

King Charles and Prince William reportedly disagree on the matter, with the current monarch once confronting William about flying with his family.

Prince George Reaches Key Milestone As Royal Rule Bars Him From Flying With His Father

George has just celebrated his 12th birthday, and with it comes the expected enforcement of a long-standing and "morbid" royal protocol.

According to tradition, once heirs reach a certain age, they're no longer permitted to travel on the same aircraft as the next in line to the throne.

In George's case, this means he may now be required to fly separately from his father, Prince William, who is first in line.

The purpose behind the rule is to safeguard the royal line of succession in the event of a tragic incident during travel.

"The Prince and Princess of Wales and their children are the future of the royal family," Royal commentator Richard Fitzwilliams told Fox News Digital, noting that the protocol serves an important purpose. "Accidents do happen, and this seems like a sensible precaution which ought to be observed, as it was with King Charles and William during Queen Elizabeth's reign."

He continued: "There are reports that the king and William, who is a pilot, disagree over this, but it should be necessary to point out that Harry is fifth in line to the throne... and only four working royals are under 70… The need for Prince George as second in line to the throne to fly separately from his father surely makes sense."

Former Royal Pilot Reveals Travel Protocol Changed When Prince William Turned 12

Charles' former pilot, Graham Laurie, previously revealed that royal travel protocols changed once William turned 12.

Speaking on "A Right Royal Podcast," Laurie recalled flying with Princess Diana, then-Prince Charles, Prince William, and Prince Harry on the same aircraft.

"After that, he had to have a separate aircraft, and we could only fly all four together when they were young with the written permission of Her Majesty," Laurie said, per Us Weekly.

She continued, "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."

King Charles Has Since Expressed His Desire For Prince George To Start Flying On His Own

British broadcaster and royal expert Helena Chard told Fox News Digital that Charles has reportedly expressed his expectation that George begin flying independently of William now that he's reached the milestone age.

"Traditional royal travel protocol expects a future heir to travel separately from their father, especially when 12 years old," she explained.

Chard continued, "Direct heirs should not fly together. Previous generations left children at home with governesses when traveling. This, however, caused a lot of upset for the children. King Charles can vouch for this; he desperately missed his parents when they were away on tour."

Chard acknowledged that William and George will likely adapt gradually to the new travel arrangement.

"This important matter is being debated as it could impact the future of the monarchy," she told the news outlet. "Travel arrangements for the heir to the throne are important at any age. And the Wales family have always traveled together… There are many rules, expectations, and traditions that the royal family is expected to follow."

Expert Says Prince William And Kate Middleton Will Adhere To The Rules' Protecting The Succession'

Royal commentator Hilary Fordwich also weighed in, noting that while the protocol isn't a formal rule, it's been consistently respected over the years.

"Rules, such as not traveling by plane or car together, now that Prince George is 12, are unwritten but a tradition," she explained. "This ensures that the next in line and heir are not lost. It has, on occasion, been relaxed or bent. Now, with the king's health issues, combined with his advanced age, it is considered extremely important to ensure Prince George's safety."

She added that William and Kate are mindful of these responsibilities.

"Prince William and Princess Catherine are adhering to many rules, especially those protecting the succession," Fordwich said. "But to a certain extent, they've reinterpreted other rules, relaxing or even disregarding others, in an admirable attempt to become a more relatable modern family. Every royal generation has likewise updated traditions, thereby remaining relevant."

King Charles Confronted Prince William Over Risky Family Flights, Biographer Reveals

Royal biographer Robert Jobson revealed in "Catherine, the Princess of Wales" that Charles once confronted William about his frequent helicopter trips with Kate and their three children.

William, who is a trained pilot, was reportedly eager to travel as a family unit, a move that raised safety concerns for the king.

According to Jobson, their differing views led to a serious discussion, culminating in Charles presenting William with "a formal document acknowledging the risks involved and taking full responsibility for his actions."

Fordwich previously noted to the publication that past tragedies have shaped this caution.

"There have been several royals who have perished in plane crashes," she said. "As a result, Queen Elizabeth II was particularly sensitive regarding who could and would be permitted to fly together. Rules were put in place years ago regarding the prohibition of royal heirs from flying together."