Early morning schedule for the tourist direct bus from Datong Railway Station to Yungang Shiku?

In the railway station, you can take the Tourist Bus Line 1 to the Yungang Shiku directly. The route is about 12 miles, and the bus fare is CNY2. The first bus departs at 07:00. The bus runs at an interval of. 12-15 mins, and the travel time is about 70 mins.

Well, I suggest you take a train not a bus. The train ride and the bus duration is almost the same, but there is convenient transportation from Yungang Shiku to the railway station and from Taiyuan railway station to the airport. After a quick glance at the caves, you should take the same bus back to the railway station, and take a train to Taiyuan. Upon arrival, take the bus No. 201 from the railway station to the airport directly. Just take your time and leave some possibility for traffic jams. BTW, the train schedule can be searched on this site.

thanks, but the train is schedued at 11.55-15.48 and the next at 14.19-20.01 only: the former is too early for seeing thoroughly the caves, the latter too late for the flight. So I would rather need to take the bus: I found that there are busses from Xinnan Station to Taiyuan at the following convenient hours: 13.10-16.20, 13.20-16.40, 13.30-16.50, 14-17.20, 14.20-17.40, 14.30-17.40: Its duration is 3h20', that is considerably less than the train: is this reliable?
How to get quickly from Yungang Shiku to Xinnan Station and then from Taiyuan General Bus Station to the airport?
Thank you!

Yes, the bus info is reliable but the duration is usually about 4.5-5 hours in actual life.
From the cave, there is no direct transport mode to the Xinnan Bus Station, you need to transfer and wait. So I suggest you take a taxi, and the fare would be CNY35 around.

Does the Taiyuan General Bus Station refer to the one located at No. 88 of Yingze Street? If so, walk about 600 yards to the nearby railway station to take the bus No. 201 to the airport.