Turkish Airlines has been playing 'hard-to-catch' with its San Francisco flight for a long time. Schedules have changed constantly for years (and without many warnings). Sometimes it was daily, then 3x a week then 6x a week. Just a random lottery.
For More Information:?Turkish Airlines Business Class?|?Costa Rica Resort?|?Southwest Airlines?|?Lufthansa Business Class?|?Istanbul (IST) via Frankfurt