Well, I guess it depends on how you mean that. (By the way, Welcome to FlyerTalk!)

Both United and American will give their top frequent flyers certificates for free upgrades that can be used in international travel, and they can be used by you or by someone else like a traveling companion.

With United, for instance, if you fly 100,000 miles on Star Alliance carriers in a calendar year and credit the miles to your Mileage Plus frequent flyer account, you will earn what they call "1K" status. After you earn that status, around the first of the next year they will credit you with six (6) Systemwide Upgrades (sometimes called "SWUs") that you can use to upgrade most fares, including international ones, if seats for upgrades are available (they hold back some seats in the hopes a paying customer will want it at the last minute, so sometimes you don't know if you will be upgraded until you actually get ready to board the flight!).

American has a similar program for what they call "VIP upgrades". It also requires you to earn a high status as a frequent flyer before they will give you the free upgrade certificates.

(Lufthansa also has a similar program, but they are less generous in handing out the upgrade certificates. If I'm not mistaken, a Senator earns two upgrades every two years, but they're limited upgrades; upgrading a transcontinental flight requires two of the "upgrade certificates", so you effectively earn enough to upgrade a US to Europe flight only once every two years.)

So you see, it takes some doing to get the free upgrades. If you were asking if any program gives you unlimited upgrades or gives free upgrades shortly after you join it, I'm not aware of any -- but if you do find one, please let me know.

Of course, most frequent flyer programs also allow you to upgrade using miles you've earned in their frequent flyer program. Although they're changing this somewhat next year, United for instance allows you to upgrade a US - Europe ticket by redeeming 15,000 to 30,000 miles each way depending on the fare you paid (and not at all for some deeply-discounted fares). Since you usually earn one mile per mile flown, with a 100% bonus if you're mid-level or higher in their Mileage Plus program, and the US-Europe flights are about 4,000 miles, that means with the 100% bonus you could earn 8,000 miles per crossing, or enough (16,000 miles) in a round trip to upgrade a "Y" or "B" transatlantic flight in the future.

And for this purpose, it doesn't matter whether the miles you redeem were earned by flying, or by buying (with a miles-earning credit card), so if you really wear the numbers off of your credit card, you may earn enough miles to upgrade all of your flights (depending on availability of upgrade seats, of course).

One final thought -- sometimes you may be able to get what we call "operational upgrades". These happen when the plane is oversold, and they need some additional seats in economy (or Business) to accommodate patrons who turn up with paid tickets. In such cases, the airline may upgrade a passenger sitting in economy to Business class, or even to First class (it has happened to me) without taking any miles or certificates, in order to free up that seat to give to another ticketholder. In such cases, airlines will often select a frequent flyer for the upgrade. So, it pays to join a program and be active in it if you're looking for free upgrades to Europe.

I hope this helps. It's sooooo much nicer in the pointy end of the plane.