The common standard where?

The common standard in the UK is that if you can stand up and want off quickly, you do, and that some people will let people go in front of them, some won't.

Not sure there has to be an etiquette or standard, just politeness.

The one thing I'd say is polite is that if you are in the aisle you don't sit there for ages if the people in the window/middle want to get out quickly, but equally if you're middle or window you need to wait for aisle, not try climbing over. The passengers concerned talking to one another about their priorities is the best way.

Neil