I know you asked this several months ago but I am having the exact same problem with a GTX 1070 as well. I however am relatively new to FSX and only have a vanilla Steam install. The only modification I have made to my install is to add "SmallPartRejectRadius=1" to my 'fsx.cfg' file in attempt to fix the problem but this hasn't helped. I am however able to see mission AI planes if I get extremely close to them, like less that 0.2nm close. This makes it all but impossible to fly some missions because you simply can't see the other aircraft you meant to be flying with. This has been an issue in all flights I'm made but I discuss it in particular in this post about the "Custom Intercept" mission: https://www.flightsim.com/vbfs/showthread.php?159493-Customs-Intercept-Mission-Missing-trigger&p=2029987#post2029987 Any thoughts as to a fix for this issue. It really is extremely annoying!