Air China is always a disaster when you fly it to Mongolia. From Bangkok your day will start with a two and a half-hour flight delay from 1 to 3:30 in the morning. If you happen to have a connecting two hours in between, you will surely miss it. Hence a ground staff will meet you upon your exit to the Beijing airport, telling you to stay put in halting English. The Air China staff tells you a lot of other stuff in Chinese but the only understandable thing is "please wait a moment". And then the lot of you are escorted to the immigration- not transit- counter, where you need to fill out and present before the immigration officer one entry card into China, a customs form and a departure form. But if you missed your flight and have no indication in your ticket that you are connecting to a later flight, the official will look for a visa, which of course you would not have because you were not planning on entering or staying in China.
So, without a valid onward ticket and no visa you will not be allowed inside the main airport area where you are supposed to arrange either an onward flight or a night in town. You will turn to your Air China staff (by this time there are several of them attending to other passengers of delayed flights from somewhere else) and ask them to speak to the immigration officer.
The immigration officer will argue with the staff and then turn to you to say "I told your attendant that if he cannot handle this situation, I shall call the manager of this airline to supervise the situation, would you like me to do that?"
They will speak some more and at length, none of which will be shared with you. "Er, yes please help me get their supervisor..." you will finally say.
There is another hour of waiting as Air China sends its staff down to assist. There are two kinds: Air China staff that deals with connecting Air China flights, and Air China staff that deal with connecting flights to other airlines. The most pissed people in the immigration area are those who missed their connecting flights on other airlines because they take the longest to process: they need to buy another ticket to show the immigration officer but could not enter the airport to do so.
Then the creativity of the Air China staff is displayed. They come down with wads of fake stickers that they put on your ticket to show that you have a valid flight to catch in transit. This is accepted by the immigration officer, even though she has already seen your ticket when you first got there! Other Air China staff come with wads of these fake stickers of fake flights that they start sticking on everybody's tickets- just to be able to pass immigration. You get an overnight stamp in your passport and you're inside!
The next problem is the overnight stay. Air China will not buy you another ticket to get to your destination on the same day so they have to provide overnight accommodation, but ground staff would feign ignorance of this at first. If a considerable number of passengers press on this matter, they will then be accompanied to the duty officer of the day, whose station is in the departure check-out counters, for which you need to fill up another baggage declaration form and go through at least two belts.
The staff assists in getting you to an airport hotel 10 minutes away, where you shall share a room with another passenger, and be provided dinner, of only boiled cabbage and rice, if you do not eat pork. Breakfast is not even mentionable.
The next morning, passengers scramble to fit their luggages into a small van which will only make one run in the morning and one in the afternoon to the airport, regardless of the number of passengers that need to fly out.
Fearing another flight delay, passengers in the boarding area stare out the large windows to make sure there is an airplane outside the gate. Once airborne however, the sigh of relief is greater than if one has gotten just a normal connecting flight in any other airport.
