'Economy Class Syndrome' is a complete misnomer in that it affects people subject to prolonged immobility be they in economy, business, first, on a bus or in a hospital bed. The problem has nothing to do with seat design and everything to do with people not leaving their seat for 12 hours. There are very simple ways of avoiding DVT on a flight such as taking a walk if possible, and if not then carrying out simple in-seat stretching exercises regularly.