Let $D$ be a non-commutative division ring with center $F$, and $G$ a
subnormal subgroup of $GL_n(D)$. Assume additionally that $D$ contains at least
$4$ elements in the case $n>1$. We show that if $G$ is locally solvable, then
it is contained in $F$. This fact generalizes the results of Stuth and
Huzurbazar which asserted that any solvable or locally nilpotent subnormal
subgroup of $D^*$ is central. Also, if $G$ contains a non-abelian
solvable-by-finite maximal subgroup, then $[D:F]<\infty$, and there exists a
maximal subfield $K$ of $M_n(D)$ such that $K/F$ is a finite Galois extension.
We also address maximal subgroups of $G$ of some special types such as
solvable, polycyclic-by-finite subgroups.