UA gives 6 certs/year good for an upgrades systemwide space avail to top tiers. Valid for most fares.
AA gives 8 similar certs/year.
DL gives some certs but these are only valid on the most expenive fares. Not useable on most fares.
US also gives a couple certs.
NW has just started a program for those who fly WAY MORE THAN TOP TIER to get a couple upgrade certs, good from any fare.
CO has no international upgrade certs; miles only.
If I remember correctly, MA atleast used to give MA elites free space available ugprades to business class transatlantic. I don't know if they still do. They are the only airline I know of that did this.
---------------------------------------------------------------------------------------------------------------
I have a related question:
Does any airline offer elites (or top tiers) free (no miles or certs) space available transatlantic/transpacific upgrades on full Y fares? B fares?