There was a group of enemies at the air port that I saw from a distance, I walked over near them, but went past them as it turns out it was a karma mission and I didnt feel like doing that. But then, they all disappeared. I guess the karma mission would after a certain distance (although I hadnt really gone that far, I was still in the air port, in that tunnel, I noticed they were gone after I climbed up the ladder. And also tagged other people in the air port but they were gone too. Then I saw some guards and 2 cars just outside the airport, so I walked over to them... then at some point when I wasnt looking, they disappeared as well, cars included.
Now I'm wondering if the reason there are hardly any enemies at the airport is because everyone just keeps disappearing.