This happened two weeks ago.
At about 1020hrs, I arrived in Beijing International Airport getting ready to leave for ChengDu – Flight NO. CA4102 1100hrs. Immediately I joined in the counter queue for check in. My turn arrived at 1030hrs but I was rejected by the counter officer because their check in system closed 30mins before the flight time. I tried to negotiate because it was only 4mins, but it did not work. So I was stranded in Beijing Airport not knowing what to do. I Was a bit panic and frustrated because the counter officer did not offer any alternative solutions as well.
So I went around asking and these were the steps taken if you happened to miss a flight in Beijing! “No sure if it applied to all airports in China”.
First, go to the ticket sale counter and ask for a change of time, I managed to change mine to 3pm. (RMB70). During the purchase ask where is the location for the registration for backup seats (后补票) – just in case if there are any empty seats in the next available flight you may be able to hop on.
Do not be shocked by the crowd at the registration counter, act like a local shout out your flight details – For example. “前往成都的后补票有吗？我要登记I” “if there any available seats for the next flight to Chengdu, I want to register!” than make your way (push,pull,elbow) to the front of the counter and give the lady your passport details. she will ask you to buy a backup ticket first, tell her you already did and she will put you on a waiting list and give you a time. I was told to come back to her at 1230hrs and see if there is available seat for me on next flight at 1300. if there is, she will take your passport, register again and give you a ticket.
if there is not, she will make a announcement at 1230hrs “前往成都的后补票一点钟没了，请等一点三十分.” “No seats available for flight at 1300hrs, please come back at 1330hrs for the flight at 1400hrs.”
In any case that the flights are full and you do not get to any backup seat. You still got your standby tickets that you brought earlier.
Lesson learn: I should have dash straight to the checkin counter and say I am late, so they will check me in first. Do not queue. Give extra time allowance for domestic travel in China as well!