SAS is spending too much money on positioning LH-crews from Oslo to Copenhagen. Just a short delay on the positioning flight or the flight to US means that you will run out of duty time if flying to Chicago, and therefore a diversion to eg. New York is required. One of the things SAS had to fight over the years with the pilot unions, but now it is over.
Another thing, is that SAS can optimise the duty time. For a long haul pilot flying 900 block hours
pr year, which is maximum only gives around 1200 duty hours, which is far from the maximum 1920 hours/year.