Whenever I access a menu after a particularly long flight, I get black screens and nothing I can do will get me back into the game (even though I can still hear audio.)I was wondering if there was a way where I can change the time of a flight without accessing the menu? Maybe even stop time (i.e. constantly stay at dawn) without accessing the menus?

There are key commands for some time related things defined. You can also set them up in the FSX options. At least, the slower and faster commands should be there (never tried them).There also is freeware and payware around to influence the time (sometimes mainly the synchronization to the rw time).But I would care more about the menu problem you are describing. Back screens and sound only show a problem waiting for a solution, not a workaround. A memory thing maybe? I don't know, sorry.