The following steps are especially useful when the loading screen bar goes up to X% then the game freezes or crashes.

CHECKLIST

Before doing anything else, please go through the loading screen checklist as the issue may be caused by missing essential application updates (such as Gaming Services) or outdated mods.

CHANGE SYSTEM LOCALE

If you're using a non-English Windows 10 set-up, change the system locale.

• In the "Type here to search" field type "Control Panel"
• Click on the "Administrative" tab click on "Change system locale" and set up Current language for non-Unicode programs to "English US" 

CREATE A NEW LOCAL PROFILE WITHOUT USING SPECIAL CHARACTERS

If you have special characters (such as à, ù, Å, ò) in your Windows Profile, create a new local user or administrator account in Windows 10 with no special characters and run Microsoft Flight Simulator from that profile.

DISABLE YOUR SECURITY SOFTWARE

Antivirus and malware checkers can close down or prevent certain applications from launching, even if they are legitimate and safe.

Stop Windows Defender from blocking Microsoft Flight Simulator by adding the launcher to the exclusions list

• Go to Start  > Settings  > Update & Security  > Windows Security > Virus & threat protection.
• Under Virus & threat protection settings, select Manage settings, and then under Exclusions, select Add or remove exclusions.
• Select Add an exclusion, and then select Microsoft Flight Simulator. A folder exclusion will apply to all subfolders within the folder as well.

Temporarily disable your security program(s) before launching Microsoft Flight Simulator

False positives occur when your antivirus software incorrectly identifies safe software as malicious. If your antivirus or anti-malware falsely flagged Microsoft Flight Simulator remove the file from quarantine if necessary then whitelist Microsoft Flight Simulator. To do so follow the instructions from your manufacturer.

• Sample of Virus & malware checkers that have been known to prevent Microsoft Flight Simulator from launching:
  • Malwarebytes
  • Trend Micro Maximum Security
  • Comodo Antivirus
  • Sophos
  • Emisoft Anti-Malware
  • Avira
  • Avast & Avast Cleanup
  • Bullguard​
    

If the sim loads normally after disabling your security program, whitelist Microsoft Flight Simulator before turning the program back on. To do so, refer to your security software's support website.

DISABLE NON-MICROSOFT APPS

3rd party programs such as backup software, tune-up utilities or resources management apps can prevent Microsoft Flight Simulator from loading fully. 

• Samples of apps and programs preventing Microsoft Flight Simulator from launching
  • Seagate Toolkit
  • Nahimic service
  • Asus Sonic Studio 2
  • Windows Audio Service
  • Garmin Express
  • WD Backup
  • Logitech G Hub
  • MSI Afterburner / Riva Tuner Statistics Server
  • EVGA Precision
  • OBS
  • Xsplit
  • Discord
  • MacType
  • Warsaw Banking App
  • Wallpaper Engine
  • A-Volute Sound studio

To investigate, please do the following:

• In the Windows Search bar, type "Task Manager" 
• Select Open
• Go to the Start-up tab
• Disable all non-Microsoft apps
• Reboot the computer
• Try launching Microsoft Flight Simulator again

If the sim loads normally after disabling non-Microsoft apps, investigate which app is preventing the sim to load.

• Enable one non-Microsoft application
• Reboot the computer
• Launch Microsoft Flight Simulator
• Enable a second non-Microsoft application
• Reboot the computer
• Launch Microsoft Flight Simulator

Repeat this process until you find the application that is preventing the sim to load. You can then disable this application or stop the process in the task manager before launching Microsoft Flight Simulator.