Two required in the summer for TATL and only one required in the Winter. The second may fly European routes in the Winter.
The OSL flights change in the Winter to EDI based in between TATL runs it seems.
I was taking to a JFK based Norwegian crew member a couple of days ago and she was transferring to SWF as it's less of a commute for her. She was saying that she had heard from more than one flight crew member that the company are talking about using 2 737MAX aircraft for the W17 season to FDF and PTP to operate the seasonal flights from there to the US. These routes have over the last 2 years been operated by a 737-800. Maybe one of them will be the redeployed aircraft from EDI.
Obviously this D8 frame could cover another route on the other three days, but this still leaves the other winter routes which vanished for the moment.
A 3 x weekly CPH possibly