I'd like to know how to give the proper speed to fly a Unity engine airplane using physical operations.

using System.Collections;
using System.Collections.General;
using UnityEngine;

public class control:MonoBehavior

{

    // Wing area wing area [m^2]

    public floatingArea;

    Rigidbody rigidBody;

    void Start()
    {
        rigidBody=GetComponent<RigidBody>();
    }

    void Update()
    {
        Vector3vec = new Vector3(0,0,0);

        //vec.z=-1;

        // Move to the left
        if(Input.GetKey(KeyCode.LeftArrow))
        {
            vec.x = 1.0f;
        }
        // Move to the right
        if(Input.GetKey(KeyCode.RightArrow))
        {
            vec.x = -1.0f;

        }
        // Move forward
        if(Input.GetKey(KeyCode.UpArrow))
        {
            vec.y = -1.0f;

        }
        // Move Back
        if(Input.GetKey(KeyCode.DownArrow))
        {
            vec.y = 1.0f;
        }

        // advance
        if(Input.GetKey(KeyCode.Space))
        {
            vec.z = 1.0f;
        }


        rigidBody.velocity=vec;
    }


    void FixedUpdate()
    {




        // Convert to local vector Convert to local vector

        Vector3 localVelocity = this.transform.InverseTransformVector(rigidBody.velocity);



        // Speed Speed

        float v=rigidBody.velocity.magnitude;



        // Get Angle-of-attack (pitch) from local vector Calculate the angle of attack (pitch angle) from the local vector

        floataoa=-Mathf.Atan2(localVelocity.y,localVelocity.z)*Mathf.Rad2Deg;



        //------------------------

        // ▼ Lift

        //------------------------



        // Lift coefficient (simple version)

        float cl = aoa*0.1f;



        // Calculate lift lift

        float lift = CalculateLiftOrDrag(cl,wingArea,v);



        // Calculate lift direction (normalized) vector lift vector

        Vector3 liftVector=Vector3.Cross(Vector3.Cross(rigidBody.velocity, this.transform.up), rigidBody.velocity).normalized;



        // Apply lift lift

        rigidBody.AddForce(liftVector*lift);



        //------------------------

        // ▼ drag

        //------------------------



        // Drag coefficient drag coefficient (simple version)

        float cd = Mathf.Clamp01 (0.005f + Mathf.Pow (Mathf.Abs(aoa)*0.0315f,5));



        // Calculate drag drag

        floatdrag=CalculateLiftOrDrag(cd,wingArea,v);



        // Calculate drag direction (normalized) vector drag vector

        Vector3dragVector=-rigidBody.velocity.normalized; // Just normalizing the inverse vector of the velocities



        //------------------------

        // ▼ Apply force

        //------------------------



        // Apply drag lift

        rigidBody.AddForce(dragVector*drag);

    }





    // COMMON METHOD FOR CALCULATING LIFT AND RESISTANCE

    public static float CalculateLiftOrDrag (float coefficient, float surface, float velocity, float airDensity=1.293f)

    {

        float q=0.5f*(velocity*velocity)*airDensity;// dynamic pressure

        return q*surface*coefficient;

    }

}