Planes are made heavy, for the same reasons as trains: safety enhancement and cost reduction.<p>Ever notice how every wheelie cart on a plane has not one but two locking handles to secure it?  How about the ram air turbine [1] which is used almost never but weighs hundreds of pounds?  Seat frames are still made mostly of metal, whereas if weight were the only consideration they would probably be carbon fiber.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Ram_air_turbine" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Ram_air_turbine</a>