xans fly, but could not reach your feet if you flew

src/mhitu.c

@@ -1206,9 +1206,8 @@ register struct attack *mattk;
         /* This case is too obvious to ignore, but Nethack is not in
          * general very good at considering height--most short monsters
          * still _can_ attack you when you're flying or mounted.
-         * [FIXME: why can't a flying attacker overcome this?]
          */
-        if (u.usteed || Levitation || Flying) {
+        if ((u.usteed || Levitation || Flying) && !is_flyer(mtmp->data)) {
             pline("%s tries to reach your %s %s!", Monst_name, sidestr, leg);
             dmg = 0;
         } else if (mtmp->mcan) {