Just thinking.. as I have to renew my passport..and where I need to update the number. . Airline sites, global entry..any place else? Why does the number need to change. Does the number changing mean it's a more or less secure document. If it didn't change, it would make it easier to connect visas from an older passport and maybe no need to carry multiples. And what happens in renewal? Not the physical book, but what info is validated? Why does it take so long? I've had passports for a long time, and I don't like to be without..so I'm asking. .