S-H has it right. As Pax (most of us) are useless. Those that have not travelled before/very often arrive very late or very early. Those travel often, think that they can ignore all the rules. These two points have an infinite length of damp string between them!!
Boarding by row? If only we would.
The bit that irritates me [jumping on the bandwagon] is that most wide body (twin aisle) a/c are boarded through a single door. Sometimes a 744/340 is boarded through two but the second door is for Biz/Upper/1st and so not many folks go through.
The time delays introduced by boarding in this way are enourmous. I have often seen a 744 boarded, efecctively, one person at a time until 350 have done so. I'll bet that, when the 380 comes and they board through two doors (one per deck) it will still be as slow. They should use two doors per deck.
I suspect that companies want to save money on gate staff and air-bridge operating staff. But then, I am a very nasty person!
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"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.