Jump/FallDown animation plays only once

When I press the Jump key, the Jump animation clip plays, (and for some reason) the FallDown clip immediately after. However, when I press the Jump key again, nothing plays. What's causing this? Also, how do I make the FallDown clip play only when my character touches the ground after the Jump?

Here are my scripts (with some lines from the beginning/end of the script not necessary to show):

Controller:

 //Move the controller during the fixed frame updates
 function FixedUpdate()
 {
     if(!isControllable)
         Input.ResetInputAxes();
     else
     {
         if(grounded) 
         {
             //Since we're touching something solid, such as the ground, allow movement
             //Calculate movement directly from input axes
             moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
             moveDirection = transform.TransformDirection(moveDirection);
             moveDirection *= walkSpeed;
             moveDirection.y -= gravity * Time.deltaTime;
             
             //Find rotation based upon axes if need to turn
             moveHorz = Input.GetAxis("Horizontal");
             if (moveHorz > 0)    //Right turn
                 rotateDirection = new Vector3(0, 1, 0);
             else if (moveHorz < 0)    //Left turn
                 rotateDirection = new Vector3(0, -1, 0);
             else    //not turning
                 rotateDirection = new Vector3(0, 0, 0);
             
             //Jump controls    
             if(Input.GetButton("Jump"))
             {
                 if(Input.GetButton("Run") && Input.GetButton("Jump"))
                 {
                     moveDirection.y = jumpSpeed/3;
                 }
                 else
                 {
                     moveDirection.y = jumpSpeed;
                 }
             }
             //Aplly any boosted speed
             if(Input.GetButton("Run") && Input.GetAxis("Vertical"))
             {
                 if(MoaliaStatus.stamina > 0)
                 {
                     isRunning = true;
                     if(MoaliaStatus)
                     {
                         moveDirection *= runSpeed;
                         MoaliaStatus.stamina -= MoaliaStatus.runUsage * Time.deltaTime;
                         isRunning = true;
                     }
                 }
                 else if(MoaliaStatus.stamina <= 0)
                 {
                     isRunning = false;
                 }
             }
             
             if(MoaliaStatus)
             {
                 if(MoaliaStatus.stamina <= MoaliaStatus.maxStamina)
                 {
                     MoaliaStatus.stamina += MoaliaStatus.staminaRecharge * Time.deltaTime;
                 }
             }
         }
     
         //Crouch the controller
         if(Input.GetButton("Crouch"))
         {
             controller.height = crouchHeight;
             controller.center.y = controller.height/2;
             moveDirection *= crouchSpeed;
             isCrouching = true;
         }
         
         if(Input.GetButtonUp("Crouch"))
         {
             //Reset height and center after ducks
             controller.height = normalHeight;
             controller.center.y = controller.height/2;
             isCrouching = false;
         }
         
         if(Input.GetButtonUp("Run"))
         {
             isRunning = false;
         }
         
         //Apply gravity to end jump, enable falling, and make sure he's touching the ground
         moveDirection.y -=gravity * Time.deltaTime;
         
         //Move and rotate the controller
         var flags = controller.Move(moveDirection * Time.deltaTime);
         controller.transform.Rotate(rotateDirection * Time.deltaTime, rotateSpeed);
         grounded = ((flags & CollisionFlags.CollidedBelow) != 0);
     }
 }
 
 //----------------------------------------------------
 function IsMoving()
 {
     return moveDirection.magnitude > 0.5;
 }
 
 function IsRunning()
 {
     return isRunning;
 }
 
 function IsCrouching()
 {
     return isCrouching;
 }
 
 function IsGrounded()
 {
     return grounded;
 }
 

Animation:

 function Update() 
 {
     //On  the ground animations
     if(playerController.IsGrounded())
     {
         animation.Blend("FallDown", 0, 0.2);
         animation.Blend("Jump", 0, 0.2);
 
         //If Running
         if(playerController.IsRunning())
         {
             animation.CrossFade("Run", 0.5);
             animation["Run"].speed = 4.4;
             nextPlayIdle = Time.time + waitTime;
         }
         else if(playerController.IsCrouching())
         {
             animation.CrossFade("Crouch", 0.2);
             nextPlayIdle = Time.time + waitTime;
         }
         //Fade in Walk
         else if(playerController.IsMoving())
         {
             animation.CrossFade("Walk", 0.5);
             animation["Walk"].speed = 3.2;
             nextPlayIdle = Time.time + waitTime;
         }
         //Fade out walk and run else
         else
         {
             animation.Blend("Run", 0.0, 0.3);
             animation.Blend("Walk", 0.0, 0.3);
             animation.Blend("Crouch", 0.0, 0.3);
             if(Time.time > nextPlayIdle)
             {
                 nextPlayIdle = Time.time + waitTime;
                 PlayIdle();
             }
         }    
     }
     //In air animations
     else
     {
         if(Input.GetButton("Jump"))
         {
             animation.CrossFade("Jump");
         }
         
         if(!playerController.IsGrounded())
         {
             animation.CrossFade("FallDown", 0.5);
         }
     }
     
     //Test for idle
     if(Input.anyKey)
     {
         if(moveDirection.magnitude <= 0)
         {
             animation.CrossFade("Idle");
         }
     }
 }