I'm planning on flying to LA with Qantas soon and the flight planner on the site states that we'll be flying on a Boeing 747-400. I was wondering if i would be able to move seats to the upper deck after take-off if there is a spare seat. I only want to do this because I want to see how it is on the upper deck.
Sorry, not going to happen: on all Qantas 747s, the upper deck is business class only. See SeatGuru for details.
You're generally welcome to swap seats in economy class after takeoff though.