[clintonb]

This is pretty easy to comprehend.

1. Some people are just ignorant and refuse to follow directions. Despite being in the final boarding group, they are the first to stand and attempt to board the plane, thinking they can somehow jump ahead. These same people would probably attempt to jump ahead of a long line at door 1 by boarding at door 2, causing delays and frustration.

2. I doubt jet bridges are cheap. Unless there is a simple way to retrofit them, all of them would need to be replaced to support dual door boarding. Sure, this might lead to slower boarding times; but, the airlines would pay for the jet bridges by increasing airfares. The airlines would also lose out on early boarding passes some customers purchase.

Overall, the benefit--let's be generous and say a 50% decrease in boarding time to 15 minutes--is simply not worth the costs to airports, airlines, and passengers. Compared to the 15-30 minutes of waiting for security, 1-2 hours of waiting at the gate to board, and 1-20+ hour flight, the 15-30 minute (1 hour for international?) boarding time is somewhat negligible.

[mtam]

I get it that there is an infrastructure cost but shorter turnarounds seem to have worked for Southwest: http://www.cnbc.com/id/43768488

A 15 minutes reduction each way on a busy route might allow the company to run an extra leg or two.

[Aqwis]

You don't need another jet bridge to board through two doors. At my local airport, the passengers seated at the back of the plane walk out of the jet bridge and across the tarmac to board through the back door.