I started having the same problem last Friday.
Maybe because I started flying to and from more demanding (bigger) airports.
Sometimes the sim would crash on approach and sometimes when starting a flight at one of those airports.
The blue bar would go almost all the way when loading a flight then I would get a CTD with no error message.
After spending the entire weekend trying different things I was able to "fix" it.
I don´t know if this will help you but it solved my problem.
I changed my virtual memory (paging file size) in Windows 10 to "custom size".
This is what I set it to: the amount of ram you have x 1024 x 1.5 for the lower value and the amount of ram you have x 1024 x 3 for the upper value.
In my case: 16 x 1024 x 1.5 = 24576 and 16 x 1024 x 3 = 49152.
I had read somewhere both values should be the same and that was what I had but since I made the change I haven't had a CTD and I am able to start my flights at any airport.
I don't know if this is what you should have set it to but I'm happy with the result.
Perhaps you can try.