To start off I would like to say that xPlane is a fantastic simulator, in my opinion, better than any other simulator ever created. Despite this fact, my xPlane 11 causes me a lot of problems. First of all, some bugs occur during my flights, which is very frustrating since the hour I spent setting up the plane was useless. One of whom is that the the world suddenly becomes entirely blue and there is no sign of land, even though being at low altitudes. Thanks to this problem, I cannot see the runway during landing and neither the airport. Another problem is that FPS are very low (sometimes even 20 FPS) and my computer (an iMac) is, modestly, very powerful: an Intel Core i7 CPU with 4,2 GHz; 30 GB of RAM and 8 of VRAM; and 2TB of disk space. I tried every solution, e.g.: lower the graphics, but they seem to not work. Can somebody help, please?