Why is it that aircraft engines are always (mostly?) rated in thrust whereas most other heavy equipment I can think of (e.g. ships, earthmovers, etc. ) is mostly spoken about in horsepower. First, am I right in my observation. If so, is this merely convention? Or does it make more sense to speak of lb of thrust for a plane and hP for a ship? I've heard of bollard pull for tugs or tractive force for locomotives but never the converse i.e. no one mentions the hP for a jet engine.