stevelup wrote:A good chunk of that flight was at 12000 feet and I didn't notice any side effects.
I spent a fair bit of timing cruising around 12,000ft last autumn and tended to think I was absolutely fine too. It was mainly flying in long, single straight lines with the aircraft trimmed out. Then, I heard a mildly amusing exchange on ATC and was laughing for about 5 minutes, which rather gave me pause for thought. Bear in mind that hypoxia can be very insidious, and one of the most common initial symptoms is euphoria.