In my quest to try to find out why my father chose to spend his military leave time in Adelaide rather than Darwin (he was stationed at Fenton Field May 1943), it was suggested to me that Darwin was hit pretty hard by earlier Japanese air raids with significant damage and many civilians evacuating the city by 1943. Thus, the city was pretty much a "shell" of what it had been.
Being in the Air Corps, it probably wouldn't have been very difficult to hitch a ride on a cargo plane and be across the continent in a few hours. I just found it odd that a man with a 2 or 3 day pass would choose to travel this far.
How much was Darwin deminished by those raids? How big a city had it been previous? Any truth to my earlier assumption? Obviously, I'll never really know why - just speculation.