[sokoloff]

Airlines I've flown publish and abide the door-closing time. (For Delta domestic flights, it's 15 minutes before scheduled departure, 30 for int'l. I think they put 20 minutes on domestic boarding passes as a buffer against watch skew arguments.)

I've seen the gate agents paying scrupulous attention to that, to ensure they don't close the gate early if any pax who have checked in haven't boarded.