Old Fella
L337, Just which jump seats are you referring to?
If I may answer on his behalf, my company's 747-400 have 4 cabin crew seats on the upper deck, 2 by the exit lanes and 2 at the top of the stairs. The cabin crew occupy the 2 exit seats for t/o and landing, thus leaving the 2 (non exit) positions available for anyone able to help themselves.