Quick update: I just booked TK (instead of LX) SIN-IST-SFO in J. Trip isn't until next Feb, and I was told seat assignment is not possible until 100 days prior to travel.

We'll have a 8-hr layover at IST and am considering the free transit tour. Has anyone done them? We've been to Istanbul many times before, but this may be a good way to spend a few hours away from the TK lounge, as good as it is.

I can't seem to find anything about "transit visa". Do we have to buy a tourist visa? And if so, can this be done right before the transit tour commences, or must we do so in advance online?