Recently took advantage of a juicy ex-ARN to SE Asia fare and looking to purchase the positioning flights (although in reality will probably wait for a sale).

Looking to travel NCL-LHR-ARN in ET and back in CE which will tip me into Silver right at the beginning of my TP year.

I select 'Business' on the flight selection page, however the final itinerary page states the ARN-LHR sector does not have CE and it offers me an O class ET fare before connecting on to a CE LHR-NCL.




However if I try and book it as a single flight, CE is available:



Is this some odd quirk of the booking system? Worth giving a call?