Originally Posted by
UpgradeMe
Presumably if you're at the gate, boarding pass in-hand and they're making final boarding calls at 20 mins before departure, they would certainly count you as a no-show if you weren't responding to PAs, and possibly clear stand-by pax to your seats if you didn't let them know you were there and waiting for some reason. Though I've seen flights depart 10-15 mins early, being at the gate 30 mins prior to scheduled to departure every flight isn't entirely necessary.