When one takes a glance at the British royal family, it may appear that they have it all, but when the conversation is about freedom of choice,  they instantly fall short. Including when it comes to how they choose to travel. 

There are many rules family members must follow to stay in Her Majesty's good graces. From not being allowed to eat shellfish or going to bed before the Queen. And, there's one another rule they must follow, and that is to avoid flying on the same plane together ever. 

There is an unwritten rule that the senior members of the royal family have to avoid traveling together on one plane just in case any tragedy strikes. This technically means Prince William should never travel on the same flight as his father or any of his own children, for that matter As reported by Business Insider. 

However, that rule became slightly inconvenient for William and his wife, Kate Middleton, as traveling separately from three small children would be rather difficult. So, in 2014, after the birth of Prince George, William and Kate asked for the Queen's special permission to fly together for their tour of Australia.

"They had to ask the Queen for permission, but she said yes," the royal press office said to BBC's Newsround. The spokesperson also told, "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."

The report further said, the likely reason the Queen felt it was okay to say yes then is because flights have become increasingly safe over the last decades, much more so than when this royal rule was implemented.  

Of course, Prince William, Kate, and the kids — including George and his younger siblings Princess Charlotte and Prince Louis —  have all been traveling together since 2014, meaning this rule could soon be erased from existence. But, maybe they should continue asking Queen Elizabeth for permission just in case.