Originally Posted by ethernal

Uh.. what? The gate agent and boarding pass scanner is not the bottleneck. The bottleneck is the people on the planes and trying to get settled. And unfortunately Delta's boarding process (as is the process for most legacies) is the most inefficient in for throughput as a result of their priority boarding process.

Everyone is always in contention for the same seats with priority boarding. PREM fights for first class seats, SKY fights for the same set of seats, and Zone 1 generally fights for the same seats (preferred). And to add insult to injury, once they finally start to fill up the back of the plane, they get interrupted by trying to in-fill the middles.

Point is, boarding PREM to Zone 1 together will always be faster than boarding them separately. In general, boarding Zone 2 followed by Zone 1 and then a mix of SKY/PREM would probably be even more optimal (not even getting into more efficient structured boarding processes).