Here's a short update on recent air travel experiences in the US.
I've just returned from a 3 weeks in the US, involving two (long) international flights and a bunch of domestic US flights.
In the US, xPAP machines now need to be removed from travel bags and put through the scanner in one of the trays provided at the check point (similar to laptop computers etc).
On all the checks I just pulled out the flow generator and put it in the tray, leaving the humidifier, cables, tubing, card reader, mask etc in my xPAP carry bag. Only at San Francisco did TSA take any interest in what I had left in the xPAP carry bag.
My xPAP machine was "swabbed" after scanning by TSA staff on 5 occasions, including when departing the US on the return international flight from San Francisco. This adds what can often be an already lengthy time taken to go through the normal security checks, but otherwise caused no problems in itself.
Finding space in the overhead lockers on US domestic flights continues to be an issue, so I advise being on the more pushy side in terms of boarding as early as you can and getting your CPAP carry-on into an overhead locker. I was mostly travelling on American Airlines before the recent $15 additional checked baggage charge came into effect, so I can see this getting even worse in future, as more US airlines introduce checked baggage charges and US travellers tray to avoid checking baggage.
I didn't make on flights on Virgin America on this trip (as their route network is still quite limited), but my daughter who works in Los Angeles for the Australian Government does when she can in the course of her business travel in the US.... and she tells me that there are 120V mains power outlets at all seats on Virgin America aircraft.
Lastly, I used my S8 running from my previously described battery packs on both ~14 hour international QANTAS flights without any issues.