  In the focus of this paper is the operation of edge contraction. One can show
that simplicial 3-polytope is flag iff contraction of any its edge gives
simplicial 3-polytope. Our main result states that any flag simplicial
3-polytope can be reduced to octahedron by sequence of edge contractions. Using
this operation we introduce a partial order on the set of flag simplicial
3-polytopes and study Hasse graph of corresponding poset. We estimate input and
output degrees of vertices of this Hasse graph.
