Update:
Last night I installed update 1.15.7.0 (cleaned the community folder for this), then loaded a 6000+ long haul flight. Used the 747 and had no issues. No CTD throughout the flight.
After I reached cruise altitude, I remembered to see if my settings have been changed from the update and they were. The settings got changed (sorry, cannot upload the photos at the moment). I plan to change them back to Ultra with terrain level of detail and objects level of detail set to 150 with 3 mods loaded (settings when the 747 would CTD). Will post an update to see if the sim update is what fixed the problem after another long haul test flight. Uploading: 20210414_125615[1706].jpg…