Several folks have answered the question about what turns are. Both morning and afternoon turns will typically have one leg where the sun is down. We also have week on/week off sort flying that is characterized as day vs night sort. If you are flying the day sort on the MD, you will typically wake up early on a coast in order to land at SDF by 11 am local time. You sit the sort for 2-4 hours, than fly to the other coast and hit the hotel. The night sort is the same, but the sort is in the middle of the night instead of middle of the day. Some of these week on/off trips have a commercial DH on one or both ends which makes them popular with commuters. The seniority required to hold a given line type fluctuates throughout the year. Due to the MD being used as a shock absorber for the international network the last couple years, our bidpack composition has changed significantly between bid periods. International flying is neither day nor night flying, but can be all in daylight/darkness or some of both and is essentially no different than international at a pax carrier. Hope this answers your question.