I booked IST-NRT on TK in J for August a couple of months ago. They seem to release 3 seats in J per flight and 4 on BKK-IST flights. Oddly enough, there has been ZERO seats released for August on the LHR-IST route in J or Y. So right now I have LHR-ZRH-IST-NRT on LX/TK but I keep checking for the LHR-IST direct flight to open.