Cold Weather flight in Northend...which Level?

Hi all,
pls forgive my stupid question...but which level has a player to be to be able flying in Northend?
Level 80 as long as you don't have a level 80 char on the server or the account?
I have 2 80s on Icecrown and was playing a Toon on Lordaeron and saw a level 74 player using a flying mount.
How does this work? I am really confused now. If I remember right you're toon has to be level 77.
Many thx and kind regards

you can buy the book on 1 character and mail it to another, so you can fly in northrend as soon as you get there.

thx for your input!

learning from trainer: you need lvl 77
learning from tome of cold weather flying: you need lvl 68
buying tome of cold weather flying: you need lvl 80