My wife’s parents are Chinese and older than 80. When they travel by air, like from Kunming to Beijing for medical treatment, they are required to be accompanied by a close relative and to have a legitimate health, etc. reason to travel. Generally it is my wife’s older brother who accompanies them. I say “required” because this is what my wife tells me, though I have never heard of such a regulation. She says the age threshold for such requirements is 70.

Can anyone here confirm this? I wonder if the same applies to those of us who are expatriates living in China. If so, this will seriously affect my domestic travel in a few years.

Never heard of any restrictions, other than what individual circumstances may require.

For example China Southern website mentions this:

"
1.What is the elderly service?

Mobility-impaired passengers over the age of 65 who even cannot board the plane without aids and certain special care or services may be treated as special passengers entitled to special services.

2.Is the elderly service charged?

Elderly tickets are priced the as regular adult tickets. If an elderly passenger needs to be escorted by an attendant assigned by China Southern Airlines, in addition to the regular adult ticket price, a service fee of 50% of the adult ticket price will be charged.
"

In my experience, generally speaking in cases like this it is not so much what any official entity requires, but what the individuals feel they need to do to avoid extra fees.

I'm over 70 & there have never been such restrictions placed on me since I turned 70. All my flights since then have been either into or out of the country, however, not within it.

I've had 4 trips out of China and 3 back in since I turned 70.

I'll have that 4th back in another week.
I can walk under my own power so that would make a difference.

I did notice quite a lineup of attendants with wheelchairs at the door of our plane on arrival in Hong Kong 2 weeks ago.

My Chinese father-in-law is over 80, and while the travel agent selling the plane ticket recommended getting a certificate of health from a reputable hospital prior to travel, in actuality no one asked to see said certificate.