First flight cover

I like the map on this Swedish cover with the flight path from Malmo to Lulea. Such covers are of interest to aviation collectors but this is part of my collection of Norwegian censored mail. The letter was sent from Lulea to Oslo in 1944. After 1943 due to staff shortages about every tenth letter was examined then sealed and dispatched uncensored, but the pencil marks on this front meant someone thought this merited further examination.  A chemical test for invisible ink was done on the reverse thus the blue streak of copper sulphate (see extra). It was opened on the left side and sealed with censor tape and tied with the red handstamp and we suppose dispatched to the addressee