Originally Posted by
invisible
The flight can be from IST, FRA or MUC with TK or UA/LH.
That completely changes the question. At LAX, TK and LH use TBIT and the connection to T7 can be annoying and involve a fair amount of walking. At SFO, LH and TK (presumably) use the G gates so the connection to UA flights is not too hard. At DEN, there is only really one terminal and I->D connections are not too bad either.