The use of the O2 mask above FL250 when a pilot leaves his/her station has changed. Effective immediately, pilots are not required to don an O2 mask on our aircraft when one pilot leaves his/her station and the aircraft is at or below FL410. However, the regulation still requires one pilot to always wear an O2 mask whenever operating above FL410. See 14CFR,121.333(c)(2)(i)(A).

About freaking time.

Not like anyone followed the old rule anyway.

Personal anecdotal experience? Mainline did. Regionals didn't.

Uhhhh, maybe more than the regionals they did, but not by much.
"They call it quick don for a reason". I've heard that a lot in the last year.

I make my own rules

Ok boomer.

You'd be surprised how many mainline didn't.

Lol my ioe instructor showed me how to make it sound like it was in use when the door was open! Quite awhile ago, but good stuff indeed.