In past threads, I've communicated that idea that all passengers have the ability to call it quits during ground stops, to the extent that a private car + air stairs will be provided to you upon request.

However, since I haven't played this card myself in 5 years, I want to provide updated info because a colleague of mine pulled the plug on his flight just yesterday.

-At the 1 hour mark, he advised the lead FA that his maximum tolerance was 2 hours.

-At the 2 hour mark, they let him escape, but chided him for resetting their take-off slot. The plane was docked at a real gate, so there was no need for air stairs or a car.

-Next, the airport people gave him a delay certificate in exchange for his boarding pass stub.

-He came back to our place here, and spent a long time on the phone with Ctrip.
*their initial proposal was to refund him his Y1000, and let him buy a new ticket for Y1600
*we were cool with this solution, but our inability to provide the boarding pass was a major snag because it was required as proof that he didn't take the flight in question

-20 minutes later, Ctrip called back to offer him a seat on any flight of his choosing without an upcharge

In closing, while I am not a Ctrip evangelist, were it not for the pressure that they placed upon MU, my colleague would: 1) need to process a refund request with MU, which can take a very long time; and 2) buy a new ticket for Y1600.