I saw this a while back on YouTube – Ghost Plane | No One in Control of this Boeing 737 | Helios Airways Flight 522 | 4K – YouTube Video TheFlightChannel: https://www.youtube.com/watch?v=Go3K0UUt2Us (about 18:10 minutes long).
I don’t know the details, but here’s the Wikipedia article: https://en.wikipedia.org/wiki/Helios_Airways_Flight_522 which indicates a loss of cabin pressurization. There was at least one person conscious on the plane. He did have limited experience. If I was in that situation, I would contact someone on the ground and ask for help since I know the plane is going to run out of gas at some point and I will die once it crashes wherever it lands.