<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Threy:
KLM ... they have their own agents in Montreal, too</font>
Quite true -- but then again NW can neither operate nor codeshare YUL-AMS flights anyway, so the only way to fly NW from YUL to Europe is to connect in Detroit or some other US airport.
This meant, fwiw, that flying to Germany from YUL one was not supposed to earn WP miles on EW flights out of AMS since these would be booked with KL-connections, rather than NW ones as required by WP.