  We call a flag variety admissible if its automorphism group is the projective
general linear group. (This holds in most cases.) Let $K$ be a field of
characteristic $0$, containing all roots of unity. Let the $K$-variety $X$ be a
form of an admissible flag variety. We prove that $X$ is either ruled, or the
automorphism group of $X$ is bounded, meaning that, there exists a constant
$C\in\mathbb{N}$ such that if $G$ is a finite subgroup of $Aut_K(X)$, then the
cardinality of $G$ is smaller than $C$.
