How can I "nerf" air-strafe-ing in this script?

I want to be able to stop the Character Controller from continuing to move at the same rate in the air. Basically, lock it to whatever direction momentum during the jump and not allow you to suddenly go backwards from the direction you're currently going.

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent (typeof(CharacterController))]
 public class P1Script: MonoBehaviour {
     public float nSpeed = 5; // Units per second
     public float speedM = .5f; // Multiplies the "nSpeed" variable to increase movement speed
     public float airSpeed = 1.5f; // Multiplies the "cAirSpeed" variable while in the air 
     private float cSpeed; // The current Speed
     public float turnSpeed = 5.0f; // Degrees per second
     public float jumpSpeed = 8; // Height of Jump
     public float gravity = 9.8f; // The rate at which gravity pulls down.
     private float vSpeed = 0 ; // Current Vertical Velocity 
     float vRotation = 0; // Prevents Pitch(?)
     public float yRange = 60.0f; // The angle limit for the Y-Axis look
     CharacterController cController;
     
     
     // Use this for initialization
     void Start () {
         Screen.lockCursor = true; // Locks Cursor to Screen; makes invisible
         cController = GetComponent<CharacterController>();
     }
     
     // Update is called once per frame
     void Update () {
         
         //Jump
             if(cController.isGrounded) {
             vSpeed = 0; // Grounded character has vSpeed = 0...
         if(Input.GetButton("Jump")) {
                 vSpeed = jumpSpeed;
                 var cAirSpeed = cSpeed / 2;
                 cSpeed = cAirSpeed;
             }    
         }
         
         // Rotation and Walk
         float rotLeftRight = Input.GetAxis("Mouse X");
         transform.Rotate(0, rotLeftRight, 0);
         var vel = transform.forward * Input.GetAxis("Vertical") * cSpeed;
         vRotation -= Input.GetAxis("Mouse Y");
         vRotation = Mathf.Clamp(vRotation, -yRange, yRange);
         Camera.main.transform.localRotation = Quaternion.Euler(vRotation, 0, 0);
         var hor = transform.right * Input.GetAxis("Horizontal") * cSpeed;
         vSpeed -= gravity * Time.deltaTime; // Applies gravity acceleration to the vertical speed
         vel.y = vSpeed; // include vertical speed in the vel
         cController.Move (vel * Time.deltaTime); // Convert vel to displacement and move the character
         hor.y = vSpeed; // Applies gravity acceleration to the horizontal speed:
         cController.Move (hor * Time.deltaTime); // Convert hor to displacement and move the character
         
         //Sprinting
         if (Input.GetButton("Sprint")) { // Check for "Sprint" as defined by project inputs
             cSpeed = nSpeed * speedM;
         } else {
             cSpeed = nSpeed;
         }
     }
 }