There are some seats on IB which go almost completely flat in the 340-300 and 340-600. I always try to get these when doing two consecutive nights on MAD Brazil day trips originating in London which seem to be a popular part of my travel plans at the moment.

Of course, if you actually know about what is flat, you have to take the 2.5 to 3 degree nose up pitch of the aircraft into account during the cruise phase of flight. Unfortunately, most of the interior designers have absolutely no idea about this whatsoever. So, you end up getting a better night sleep on a "flat-horizontal" bed by sleeping head forward.

Happy landings