when I was in Amsterdam boarding an intra-Europe KLM a few weeks ago, they basically just let all of coach on at once and it sorts itself out.
when flying back to Amsterdam from Helsinki on KLM, they had gates where you scanned your boarding pass (like getting on a subway or something) and if it wasn't your zone boarding, it wouldn't let you on as happened with the lady in line in front of me.
either of those are better options than how it works in the US now.
How is that different from zoned boarding inthe US ?