Q:

Unity 2d dropping more then 1 bomb

when I instsiate the bomb it makes more then one sometimes up to 3bombs at once I want it to make 1 bomb not 2 or 3 bombs. 
I need a way to be sure it only use the void dropbomb once.
I'm looking forward to your help I like to say sry for the bad English and maby that point that I could have missed something important in my code 
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlaneBombDroper : MonoBehaviour
{
    public GameObject bomb;
    public GameObject bombDropPostion;
    public GameObject planePostion;
    int bombDropRandomNum;
    public float[] dropPostionsX;
    bool bombIsDroped;
    // Use this for initialization
    void Start()
    {

        bombDropRandomNum = Random.Range(1, 3);
    }
    void Update()
    {
        if (bombDropRandomNum == 1 && bombIsDroped != true)
        {

            if (planePostion.transform.position.x < -2.75f && planePostion.transform.position.x > -3)
            {
                dropBomb();
            }
        }
        if (bombDropRandomNum == 2&& bombIsDroped != true)
        {
            if (planePostion.transform.position.x < -9.5 && planePostion.transform.position.x > -10)
            {
                StartCoroutine("WaitForSeconds");
                StopCoroutine("WaitForSeconds");
            }
        }

    }
    void dropBomb()
    {
        Instantiate(bomb, gameObject.transform.position, gameObject.transform.rotation);
    }
    IEnumerator WaitForSeconds()
    {
        dropBomb();
        yield return new WaitForSeconds(1);
    }
}

A:

the bombdrop function fires off a new bomb irrelevant of if there is a bomb already in action - you need to add a condition that if a bomb is firing not to run that new bomb code.  You already have the bombisdroped variable - it makes sense that if (!bombisdroped)  is then your new bombdrop function

