I always fly with my CPAP machine as carry on. As with any medical equipment or medication, if you put it in your checked luggage, then you risk having it lost.

I use my CPAP on long international flights. My CPAP is not battery powered and I always plug into a conventional outlet...of course there has to be an outlet there, or you're out of luck! You can request special seating if available. On the EWR-DEL flight, which is a 777-200, I have encountered power outlets in F that fail to work properly more than once...bummer for me!

Trying to sleep in coach sucks to begin with and using a CPAP in cramped quarters is a special form of torture, but I have done it. I have never met a flight attendant who is not familiar with a CPAP machine.

I have gotten tired of the hassle of a second TSA inspection because my CPAP got flagged in the X ray machine. While it is a pain to unpack, I always separate the CPAP from the rest of my carry on.

Good luck!