As a note, if this is single player or you have access in multiplayer, you can open the console (F1) and type debugmenu and hit enter. Close the console (F1 again). Now, press H. You will now be able to fly through things. Up is spacebar and down is CTRL by default. Once above ground, you can press H to land and then go to console and type debugmenu again to turn it off and close the console to be back to normal.
It saves having to reload the game.