Was able to discover N and E fares by coincidence, while trying to book a last second el cheapo fare to the US and it seems like N and E is available on codeshare flights operated by Alaska Airlines, at least to/from SEA connecting to NW 33/34:

Klm Royal Dutch
Flight: 7252
(Operated by Alaska Airlines)
Departs
Seattle (SEA)
December 28
3:16 pm Arrives
San Francisco (SFO)
December 28
5:21 pm Notes
Cabin class: J0 C0 Z0 D0 Y0 X0 S4 W0 E0 N0
Meal:
Distance: 678 mi
Stops: non-stop
Flight Time: 19:36
McDonnell Douglas MD-80McDonnell Douglas MD-80