Originally Posted by Threy

As pointed out by wldtrvlr already, KLM and NWA share their income and costs 50/50 on the routes across the pond to the US ( Canada is excluded as well as the Caribbean ) so it is completely irrelevant which route is served on blue or silver metal.

The agreement to share income and costs 50/50 covers all transatlantic flights to the US, Canada and to Mexico City. The caribbean is excluded. The Canadian and Mexican flights must be flown by KL as NW does not have the authority to fly those routes, just as the US-FCO, LGW, CDG and FRA had to be flown by NW (maybe KL has more authority now that they are part of AF, or less restricive EU rules?). The other rule is that overall in the JV, roughly half the flying has to be done by each airline, thanks to pilot agreements. So the flight flown and by whom are tweaked under these various restrictions. For example as mentioned by others, the DC-10 that flew AMS-IAD was switched to AMS-MEM, and the KL plane went from MEM to IAD