I must say it's a rare exception to have a Dutch speaker on NW's flights to AMS; all of my NW flights to/from AMS in the past few years have never had any Dutch speakers on board.

Delta, on the other hand, goes to the other extreme and has speakers for just about all of its international flights that use a foreign language - when they started their JFK-BOM flights, they closed their BOM base (and the speakers based there) and went out to hire brand new Hindi speaker FAs from the U.S. Every BOM flight has about 2-3 Hindi speakers currently. They also went out to hire new Hungarian, Romanian, Ukranian, Czech, Greek, and Turkish speakers for their BUD, OTP, KBP, PRG, ATH, and IST nonstops from the U.S., as well as additional Dutch speakers when they further expanded AMS...

Of the US carriers, both Delta and United have the benefit of ex-Pan Am FAs who speak a multitude of languages when they acquired PA's transatlantic and LHR ops respectively...so they did have a head start on airlines like AA or CO.