I think the best way to get a registration is to look at ACARS logs available onlime. I think you'll find that a good number of European and trans-Atlantic flights are in here (other areas have people logging too).
A valuable resource for recent flights is the WorldAcarsLogs group
. There are other links too, depending on where and when you traveled. For trans-Atlantic flights, Overflight Review Online
is another valuable resource.
Aviation Photographers & Enthusiasts--Coordinate your life.