I have the same issue with my ultra 1Got my Ultra 2 ~a week and a half ago. Charged to full the first day, and then wore it for 48 hours. Was down to around 27%%. Charged it and repeated the cycle a couple more times (recharged once at 30% and once at 26%).
Upgraded to 10.1.1 (and rebooted the watch) this morning just before leaving for the airport. Was 100% at 5:30am when I left home, 96% when I boarded my flight at 6:45am, 89% at 8:45am (after first flight) and 65% at 12:00pm (after 2nd flight). Used airplane mode on iPhone while in-flight. Listened to audiobook/music via airpods (from my iPhone); only thing I used my watch for was to check the time.
Anyone else have degraded battery on their Ultra after the update? Or does anyone notice significantly poor performance with air travel?