The "Do Not Fly" list is usually for suspected terrorists.
Perhaps it was just a name-match? The wikipedia article https://en.wikipedia.org/wiki/No_Fly_List says:
> Many individuals were "caught in the system" as a result of sharing the exact or similar name of another person on the list
However, there are at least 82 "Daniel Stenberg"s in Sweden (and I'm surprised its not considerably higher that that!) https://personer.eniro.se/resultat/Daniel%20Stenberg