For a more advanced explanation, view Kered13’s steam post on Team Fortress 2’s air strafing. Most of it applies to Deadlock.

Air Strafing¹⁾ is the act of changing direction while in the air using both your movement keys and camera movement. Air Strafing can be used to move around corners, readjust your position in the air and gain a small amount of speed.

Air Strafing in Deadlock is significantly weaker than in other Valve and Source games; the maximum you could practically do in Deadlock is a ~90° turn.

One way of Air Strafing goes as follows: first be in the air. If you are pressing the forward movement key, let go and press either left or right and move your camera in the same direction in a smooth motion.