Originally Posted by
Stranger
Let me guess here.
Following what appears to be current airline practice worldwide, to save on the fuel load, they probably had originally filed a flight plan to Tianjin (or some even closer location) with Beijing as an alternate.
So that when weather in Beijing was problematic, they could no longer afford to circle but had to land somewhere.
So far the practice has no led to any serious accident, so maybe it is actually OK. However this type of unpleasantness is a by-product.
Incidentally, this is not specific to AC.
Or, perhaps since Beijing airport's landing slots are booked to the last minute, they are not very tolerant of minor disruptions. Very small disruptions can lead to very large impacts. I seem to recall that Beijing is so busy that they have no slots left to sell and no gate time left either. So when things come off the rails, they really really go off the rails. Unless you know that the AC flight was the only one impacted like this, it seems like a bit of a wild accusation.