How to move whilst airborne (using standard third person character script)?

As I said I'm using the third person character script from the standard unity assets package (slightly modified). When I jump it uses the velocity previous to the jump to send me in a direction, I am wanting to change this so you can move mid air but I can't seem to get it to work.

 using UnityEngine;
 
 namespace UnityStandardAssets.Characters.ThirdPerson
 {
     [RequireComponent(typeof(Rigidbody))]
     [RequireComponent(typeof(CapsuleCollider))]
     [RequireComponent(typeof(Animator))]
     public class ThirdPersonCharacter : MonoBehaviour
     {
         [SerializeField] float m_MovingTurnSpeed = 360;
         [SerializeField] float m_StationaryTurnSpeed = 180;
         [SerializeField] float m_JumpPower = 12f;
         [Range(1f, 4f)][SerializeField] float m_GravityMultiplier = 2f;
         [SerializeField] float m_RunCycleLegOffset = 0.2f; //specific to the character in sample assets, will need to be modified to work with others
         [SerializeField] float m_MoveSpeedMultiplier = 1f;
         [SerializeField] float m_AnimSpeedMultiplier = 1f;
         [SerializeField] float m_GroundCheckDistance = 0.1f;
 
         Rigidbody m_Rigidbody;
         Animator m_Animator;
         bool m_IsGrounded;
         float m_OrigGroundCheckDistance;
         const float k_Half = 0.5f;
         float m_TurnAmount;
         float m_ForwardAmount;
         Vector3 m_GroundNormal;
         float m_CapsuleHeight;
         Vector3 m_CapsuleCenter;
         CapsuleCollider m_Capsule;
         bool m_Crouching;
 
 
         void Start()
         {
             m_Animator = GetComponent<Animator>();
             m_Rigidbody = GetComponent<Rigidbody>();
             m_Capsule = GetComponent<CapsuleCollider>();
             m_CapsuleHeight = m_Capsule.height;
             m_CapsuleCenter = m_Capsule.center;
 
             m_Rigidbody.constraints = RigidbodyConstraints.FreezeRotationX | RigidbodyConstraints.FreezeRotationY | RigidbodyConstraints.FreezeRotationZ;
             m_OrigGroundCheckDistance = m_GroundCheckDistance;
         }
 
 
         public void Move(Vector3 move, bool crouch, bool jump, bool run)
         {
             if (run == true)
             {
                 m_MoveSpeedMultiplier = 1.3f;
             }
             else
             {
                 m_MoveSpeedMultiplier = 1f;
             }
 
 
             // convert the world relative moveInput vector into a local-relative
             // turn amount and forward amount required to head in the desired
             // direction.
             if (move.magnitude > 1f) move.Normalize();
             move = transform.InverseTransformDirection(move);
             CheckGroundStatus();
             move = Vector3.ProjectOnPlane(move, m_GroundNormal);
             m_TurnAmount = Mathf.Atan2(move.x, move.z);
             m_ForwardAmount = move.z;
 
             ApplyExtraTurnRotation();
 
             // control and velocity handling is different when grounded and airborne:
             if (m_IsGrounded)
             {
                 HandleGroundedMovement(crouch, jump);
             }
             else
             {
                 HandleAirborneMovement();
             }
 
             ScaleCapsuleForCrouching(crouch);
             PreventStandingInLowHeadroom();
 
             // send input and other state parameters to the animator
             UpdateAnimator(move);
         }
 
 
         void ScaleCapsuleForCrouching(bool crouch)
         {
             if (m_IsGrounded && crouch)
             {
                 if (m_Crouching) return;
                 m_Capsule.height = m_Capsule.height / 2f;
                 m_Capsule.center = m_Capsule.center / 2f;
                 m_Crouching = true;
             }
             else
             {
                 Ray crouchRay = new Ray(m_Rigidbody.position + Vector3.up * m_Capsule.radius * k_Half, Vector3.up);
                 float crouchRayLength = m_CapsuleHeight - m_Capsule.radius * k_Half;
                 if (Physics.SphereCast(crouchRay, m_Capsule.radius * k_Half, crouchRayLength, Physics.AllLayers, QueryTriggerInteraction.Ignore))
                 {
                     m_Crouching = true;
                     return;
                 }
                 m_Capsule.height = m_CapsuleHeight;
                 m_Capsule.center = m_CapsuleCenter;
                 m_Crouching = false;
             }
         }
 
         void PreventStandingInLowHeadroom()
         {
             // prevent standing up in crouch-only zones
             if (!m_Crouching)
             {
                 Ray crouchRay = new Ray(m_Rigidbody.position + Vector3.up * m_Capsule.radius * k_Half, Vector3.up);
                 float crouchRayLength = m_CapsuleHeight - m_Capsule.radius * k_Half;
                 if (Physics.SphereCast(crouchRay, m_Capsule.radius * k_Half, crouchRayLength, Physics.AllLayers, QueryTriggerInteraction.Ignore))
                 {
                     m_Crouching = true;
                 }
             }
         }
 
 
         void UpdateAnimator(Vector3 move)
         {
             // update the animator parameters
             m_Animator.SetFloat("Forward", m_ForwardAmount, 0.1f, Time.deltaTime);
             m_Animator.SetFloat("Turn", m_TurnAmount, 0.1f, Time.deltaTime);
             m_Animator.SetBool("Crouch", m_Crouching);
             m_Animator.SetBool("OnGround", m_IsGrounded);
             if (!m_IsGrounded)
             {
                 m_Animator.SetFloat("Jump", m_Rigidbody.velocity.y);
             }
 
             // calculate which leg is behind, so as to leave that leg trailing in the jump animation
             // (This code is reliant on the specific run cycle offset in our animations,
             // and assumes one leg passes the other at the normalized clip times of 0.0 and 0.5)
             float runCycle =
                 Mathf.Repeat(
                     m_Animator.GetCurrentAnimatorStateInfo(0).normalizedTime + m_RunCycleLegOffset, 1);
             float jumpLeg = (runCycle < k_Half ? 1 : -1) * m_ForwardAmount;
             if (m_IsGrounded)
             {
                 m_Animator.SetFloat("JumpLeg", jumpLeg);
             }
 
             // the anim speed multiplier allows the overall speed of walking/running to be tweaked in the inspector,
             // which affects the movement speed because of the root motion.
             if (m_IsGrounded && move.magnitude > 0)
             {
                 m_Animator.speed = m_AnimSpeedMultiplier;
             }
             else
             {
                 // don't use that while airborne
                 m_Animator.speed = 1;
             }
         }
 
 
         void HandleAirborneMovement()
         {
             // apply extra gravity from multiplier:
             Vector3 extraGravityForce = (Physics.gravity * m_GravityMultiplier) - Physics.gravity;
             m_Rigidbody.AddForce(extraGravityForce);
 
             m_GroundCheckDistance = m_Rigidbody.velocity.y < 0 ? m_OrigGroundCheckDistance : 0.01f;
         }
 
 
         void HandleGroundedMovement(bool crouch, bool jump)
         {
             // check whether conditions are right to allow a jump:
             if (jump && !crouch && m_Animator.GetCurrentAnimatorStateInfo(0).IsName("Grounded"))
             {
                 // jump!
                 m_Rigidbody.velocity = new Vector3(m_Rigidbody.velocity.x, m_JumpPower, m_Rigidbody.velocity.z);
                 m_IsGrounded = false;
                 m_Animator.applyRootMotion = false;
                 m_GroundCheckDistance = 0.1f;
             }
         }
 
         void ApplyExtraTurnRotation()
         {
             // help the character turn faster (this is in addition to root rotation in the animation)
             float turnSpeed = Mathf.Lerp(m_StationaryTurnSpeed, m_MovingTurnSpeed, m_ForwardAmount);
             transform.Rotate(0, m_TurnAmount * turnSpeed * Time.deltaTime, 0);
         }
 
 
         public void OnAnimatorMove()
         {
             // we implement this function to override the default root motion.
             // this allows us to modify the positional speed before it's applied.
             if (m_IsGrounded && Time.deltaTime > 0)
             {
                 Vector3 v = (m_Animator.deltaPosition * m_MoveSpeedMultiplier) / Time.deltaTime;
 
                 // we preserve the existing y part of the current velocity.
                 v.y = m_Rigidbody.velocity.y;
                 m_Rigidbody.velocity = v;
             }
         }
 
 
         void CheckGroundStatus()
         {
             RaycastHit hitInfo;
 #if UNITY_EDITOR
             // helper to visualise the ground check ray in the scene view
             Debug.DrawLine(transform.position + (Vector3.up * 0.1f), transform.position + (Vector3.up * 0.1f) + (Vector3.down * m_GroundCheckDistance));
 #endif
             // 0.1f is a small offset to start the ray from inside the character
             // it is also good to note that the transform position in the sample assets is at the base of the character
             if (Physics.Raycast(transform.position + (Vector3.up * 0.1f), Vector3.down, out hitInfo, m_GroundCheckDistance))
             {
                 m_GroundNormal = hitInfo.normal;
                 m_IsGrounded = true;
                 m_Animator.applyRootMotion = true;
             }
             else
             {
                 m_IsGrounded = false;
                 m_GroundNormal = Vector3.up;
                 m_Animator.applyRootMotion = false;
             }
         }
     }
 }