We don't have valid ESTAs for USA. Would the plane be allowed to land with us on board, would we have to stay on plane until it departed, would we be able to go into a transit area?
I suspect this situation has been foreseen and catered for, but I'd be interested to know what the position is, especially as the weather is somewhat unsettled at the moment, and airfields as little as 50 miles apart here (UK) can be experiencing wildly different conditions.
Some years ago I spent 3 days trapped at SFO, but on that occasion we were leaving the states so we had valid docs and could go back into town to a hotel and return to the airport to try for a flight the next day. We had a good time with some other pax also stuck with standby tickets but the memory lingers.