I always find between 1 and 3 candestine jobs by checking all the magenta airports. Make sure you're zoomed in on the map so that the smallest airports show up.

 

If you don't find a clandestine job you like, change the date to reset the jobs and look again.

 

Hook

since the update I have had the AI pop up every clandestine mission at around 26NM from TD.

 

I am always at about 60ft above the water (I always fly arcs over water; as has been said it works every time) and it immediately vanishes and he always clears me straight after...bug?

 

jake

Also, try to fly when it is overcast and raining. I have yet to see an AI. I also, take an indirect route to the destination and at about 200 to 300 AGL.

I just did my first clandestine mission! I flew at night, sideways/parallel from the direct route and constanly was skimming the treetops with ALL lights off. Didn't see the AI at all. Got big points!

I experienced the best way to finish the jobs without detection is flying not the direct path.

Always make a detour and you`ll finish all of them.