He only 4 hours sleep
In the Aftonbladet story here The excuse that he gave was that he had only 4 hours sleep. He was on leg 4 of a 5 sector day CPH-ARN-CPH so had most probably been on duty about 8 hours with turnarounds.
As he must have had the minimum 8hrs hotel time, what was he up to that not only lead to only 4 hours sleep but also to be so knackered that he fell asleep?