Today, I worked out for myself the instructions that traveling bijorn offered above. If I had read them yesterday, it would have saved me a few minutes of aggravation trying to remember how invoke pairing with AirPods Pro. But the real aggravation was the overall low volume (even in NC mode on my 1st gen AirPods Pro it was on par with the United earphones) followed by the frequent dropouts. Unfortunately, I wasn't traveling with my Sony WH-1000XMs (first gen). Those generally lock onto Bluetooth sources pretty well. I had to fallback to the airline-supplied earphones, which was disappointing after I finally got a flight with the Bluetooth IFE. Oh, the humanity.