If your flight will not start because MFLink cannot synchronize with FSUIPC, check these two settings.

Flying X-Plane? Check your XPUIPC version first: see MFLink stays stuck on “Synchronization in progress” or “Boarding” with X-Plane.

Step 1: Set FSUIPC to High priority #

1. Press Ctrl + Shift + Esc to open the Task Manager.
2. Open the Details tab.
3. Right-click FSUIPC, then Set priority > High.
4. Leave MFLink at its normal priority.

Windows resets this priority each time FSUIPC restarts, so repeat it if needed.

Step 2: Do not run FSUIPC as administrator #

1. Open the FSUIPC installation folder.
2. Right-click the FSUIPC executable, then Properties > Compatibility.
3. Click Change settings for all users if available.
4. Untick Run this program as an administrator, then click Apply.

MFLink must also run in normal mode, not as administrator. Restart both, then launch your flight.

Still not synchronizing? Open a support ticket.