Something in the ground detail is causing a huge frame rate hit on my system, and I suspect is the source on similar posts on this issue. Pre patch I could expect 22-28 FPS in the tower, and near the ground. Now it is low teens to single digits. Experienced this in both the SEA and MA.
Sitting in the SEA tower with no smoke/fire/other planes displayed I got 11FPS. After sliding the detail range to .5 miles it went to 60FPS.
Nothing changed on my system other than the new patch.