I also had this performance issue on my desktop with a GTX1060 6gb no matter the resolution or graphics quality, yet it runs ok on my old laptop with a GT750m.
The framerate only drops when im flying close to the ground for example: -Desert: under the two arches -Park: when flying trough the gates -Parking lot: well.. basically it is unplayable for me except for the open area. Never had these issues with earlier versions. I'll check if a driver update solves the problem.