Turkish Airlines Miles&Smiles - IST-CPT can I get off in JNB?

I am ticketed from IST-CPT in Business. I know that the flight (TK080) also stops at JNB en-route. Would it be possible for me to get off in JNB (I would have hand luggage only) and end my journey there? Has anybody been on this flight before?, does everyone have to get off the flight in JNB to clear immigration?, if not do they check your boarding pass before you get off?

Shouldn't be a problem. Tk sells ticket IST-CPT or IST-JNB for same plane. That mean you can get off in JNB as well. And JNB has passport police.

The only thing stopping you is that there will be one passenger less than the manifest says - meaning potential issues for when the flight travels on to CPT.

Also, should you have a return ticket, this will most likely be cancelled.

As you have a Business tix, you should be able to make the change without any penalty. You should do that.