In update 6 they fixed it, but only for external view, still broken in cockpit view... sigh.

I don't mind Flight Simulator not being perfect, I don't expect it to be. But they clearly have a quality control issue at Microsoft. Every mandatory update the game just..  totally breaks. 6th update and 6th time in a row that I want to start the sim, and it's just stuck in an update that doesn't run correctly. And the bugs introduced in my opinion relatively severe that they should either be caught before the release, or quickly patched right after (like not being able to control the plane when you're panning the view around.. really?? I find the sim responding to your controller a pretty important part in flight simulation software). Between U5 and 6 we haven't even been able to play the game at all because it always crashed to desktop.

This was indeed broken (for many) in SU5.  However, I finally found a work-around that had been posted on the main MS forum:

Without the addition of an axis to the right-click mouse command there was no more viewing function.  How I made these updated assignments:

• Copy the default mouse profile (unless you've already made  your own version) so you can edit it.
• Find the Cockpit and External Camera assignments.
• You will find the Freelock modes already assigned to right-click.
• You will need to add assignments to the Yaw and Pitch Axis for both cameras

The only way I found to do this was to set the assignment from the detect mode.  I held down the right mouse button and carefully moved it in the horizontal mode, then the vertical mode for the other.  This is very difficult to control - many times the Options  system picked the wrong combination on the axis, so I immediately deleted it and kept trying until I got the assignments you see above.  Now, the Freelock views work again.

Hi guys, if you haven't found a solution, try this: Ctrl+9, then your mouse freelook is back!