Prince William and Kate Middleton had to be granted special permission by The Queen go on holiday as a family with their children in tow.
The Royals were seen at Gatwick Airport as they headed off to an undisclosed location with their children for a half term break.
The Duke and Duchess of Cambridge and their children Prince George, eight, Princess Charlotte, six and Prince Louis, three were spotted outside the family Windsor Suite at the airport, which is reserved for Royal and other high profile names.
Although there have been royal tours in the past to Canada, Poland and Germany, this could be one of the last times the family travels as a group.
In order to protect the Royal lineage, there is a rule that says senior members are not given permission to fly together unless Her Majesty approves their journey.
The rule will affect the Cambridge families moves in the future, in particular when George turns 12 to lessen the risk of a family tragedy.
At that age George who is third in line to the throne he will need to fly in a separate plane from his dad who is second in line to the throne.
Charles and William cannot fly together, nor can Charles and the Queen.
The Queen has bent the rues in the past allowing William to fly with his nine month old son and family to Australia and New Zealand in 2014.
In September 2016, William and Kate also headed to Canada with George and Charlotte.
And in July 2017 The Cambridges went on a tour of Poland and Germany - taking three flights together.
In December 2014 when they travelled to New York their young son remained at home with his nanny and grandmother Carole Middleton.
A spokesperson from The Royal Family’s press office told 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 travelled together in the past, it is something that the Queen has the final say on."
The family's destination this time is unknown but they may have flown to Greece for the wedding of Princess Diana's godson Prince Philippos and Nine Flohr.
Their nanny Maria Teresa Turrion Borrallo also joined them at the airport.
