Humm...
Looks to me like only one option to cut down on multiple transshipments
BA London-Seattle
AS Seattle-Anchorage
Means under the floor on the BA sector & then the AS sector is 737-combi
You may find that it is cheaper to arange everything as excess baggage !!
This used to be permitted outbound UK, but NOT inbound.
The only other option is to check with Martinair to see if they are running their "Noah's Ark" operation ((used to run in winter months only AMS-PIK-ANC-HNL-AKL-SYD))
Is this for the Itadrodt (or whatever it's called))
G