same thing happened to me and i posted this back in 2004....
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i had that happen last year on a flight from las to sfo with me parked in 3c on a 737*. we were "rolling" and it happened seconds before rotation. the poor f/a got up and tired to fight the g force and close the door but to no avail. now as for me, i unbuckled and swung my legs across the aisle and up against the side of seat 4c until she was able to get the door closed after we leveled at 3k ft.

after all was said and done, i was asked by the f/a why i did what i did with my legs and simply told her that "it's my house as well" and that i'd do it again if need be.

now, this is what got me-i did what i did because i wanted to and upon deplaning, i was personally thanked by the 3 f/a's, the captain and the f/o but when i entered the terminal at sfo, i was met at the gate a supv who presented me with $500 worth of travel certs. (think the capt. made a call while in flight)

talk about being blown away for just looking out for "my house"
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*ahhhh, the pre-theodore daze....