Better safe...

Did you know that, here in the UK, there's an unwritten rule that heirs to the throne should not fly together in the same plane?  The reason is obvious, even if something we'd rather not think about.  As a matter of practicality, the rule is not enforced where small children are concerned.  So William, George and Charlotte have flown together, although there will come a time, when they are older, when this will not be allowed.