Originally Posted by eigenvector

And hence narrow body preferred seats = zone 5 so you can have legroom or bin space but not both.

Originally Posted by macleod199

I think exit rows are Zone 3 as well, which makes some sense.

Speaking as an operational research person, the problem with any 'ideal' boarding method will always be that pesky reality gets in the way. The blowback from splitting up families wanting/needing to board together would likely cause more delays than trying to optimally interleave people. You're never going to get even close to perfect once you bring in the real constraints.

I agree with the line of thought that even half-hearted enforcement of carry-on rules at check-in would probably make the biggest difference to AC boarding at this point. Or bringing back domestic free first checked bag.

I also agree with the line of thought that for AC the objective is more about making people feel rewarded (with the ultimate goal of maximizing profit) than other forms of efficiency. An obvious example of this is that Zone 2 people are often in preferred seats near the front, and so when Zone 3 starts boarding a few of them are often still getting sorted out and blocking the aisles. Not about boarding efficiency at all.