Delta and KLM have Amsterdam on sale for $482 round trip from mid-November to mid-December and $487 for January to March 2017 for nonstop flights. This fare is even available for Thanksgiving week travel.
Delta Airlines New York JFK – Amsterdam AMS nonstop
$481.36 round trip Sat Nov 19 – Sun Nov 27 (Thanksgiving Week)
Delta had this same ticket price offer on August 8.
Google Flights shows KLM operated nonstop flights have same fare as Delta, yet the tickets I priced rise to mid-$700s on KLM site. They are available through Delta for $486.36 fare, even for all KLM operated flights.
Delta ticket for KLM-operated flights New York JFK – Amsterdam AMS nonstop
Loyalty Traveler curated Airfare Deals.