(c) Vulnerability to A.A. fire or Fighter attack. Troop carrying aircraft or gliders are comparatively slow moving, and without the power to manoeuvre possessed by either bombers or fighters. For a successful landing without prohibitive casualties they are therefore dependant on effective air superiority, distraction of the enemy's air force, or the concealment provided by night travel. 4. Parachutists. (see Periodical Notes on the German Army No.19) (a) These have the advantage that they are quick to land from (b) aircraft and are independent of landing grounds, most open spaces being suitable for them.