AMS is a very large city for Delta. Wikipedia is nonrev travel's best-kept secret (I can't count how many times I've suggested it here) - there's a page dedicated to destinations served by Delta, and you can go to any airport's page to see which destinations go along with which cities. Delta Air Lines destinations - Wikipedia, the free encyclopedia

Keep in mind, summertime is a very scary time to nonrev to Europe. Especially on a buddy pass. You may think that if you were just past cutoff and didn't get on a flight, you'll be on top of the list for the next flight, right? Nope. Each flight is treated 100% independently, and there's no special treatment for those that have been waiting for days.