Just got off a flight (ewr-iah), was told by the EWR based FA (rather rudely) that I had to keep my armrest down during the flight. I am referring to the armrest facing the aisle in an aisle seat, not between the seats. I discovered that you could lift the armrest most of CO mainline planes a few years ago and other than being told a few times on takeoff & landing that it had to be down, I have never had anyone question this. I asked the FA if it was a FAA reg, after hesitating she said yes so I put it down.

If it is an FAA reg CO has done a poor job of enforcing this, does anyone know if it is?

Thanks.