Originally Posted by rickair7777

You cannot drink on duty of course.

But layovers are not duty, they are rest.

The FAA rule is no alcohol less than 8 hours prior to duty. US airline rules vary from 8-12 hours. So on any longer overnight you can have a beer or two with dinner, if you're there for 30 hours you can even party it up on the first night if you want.

In the old days (15+ years ago) it was very common to push the limits of the rules, and even more common to show up hung over. Today that's far less common, folks who do that are considered to have a problem.