Deep copy of Object array that includes multiple classes in Java?

Question

I'm currently struggling to create a deep copy of my Object array in Java. This Object array includes values from three different classes, with only one of these classes being a subclass of the other. The classes are listed as follows:

//First superclass
package Plane;
public class Plane {
    
    
     private String brand;
     private double price; 
     private int horsepower;
    
     
    public Plane() {
        brand = "test";
        price = 50000.99; 
        horsepower = 500;
    }
    
    public Plane(String planeBrand, double planePrice, int planePower) {
        this.brand = planeBrand;
        this.price = planePrice;
        this.horsepower = planePower;
    }
    
    public String getBrand() {
        return this.brand;
    }
    public void setBrand(String planeBrand) {
        this.brand = planeBrand;
    }
    
    public double getPrice() {
        return this.price;
    }
    
    public void setPrice(double planePrice) {
        this.price = planePrice;
    }
    
    public int getPower() {
        return this.horsepower;
    }
    
    public void setPower(int planePower) {
        this.horsepower = planePower;
    }
    
    //COPY CONSTRUCTOR
    public Airplane(Plane plane) {
        this.brand = plane.getBrand();
        this.price = plane.getPrice();
        this.horsepower = plane.getPower();
    }
    
    public String toString() {
        return "The airplane is manufactured by " + this.brand + " and costs $" + this.price + ". It has " + this.horsepower + " horsepower.";
    }

    public boolean equals(Plane plane) {
        if (!(plane instanceof Plane) || plane == null) {
                return false;
            } else if (this.brand != plane.getBrand() || this.price != plane.getPrice() || this.horsepower != plane.getPower()) {
                    return false;
                } else {
                    return true;
                }
            }
        }

//Second class
package Boat;
public class Boat {

    private double weight;
    private double price;
    
    public Boat() {
        weight = 3949.5;
        price = 64000;
    }
    
    public Boat(double boatWeight, double boatPrice) {
        weight = boatWeight;
        price = boatPrice;
    }
    
    public double getWeight() {
        return this.weight;
    }
    
    public void setWeight(double boatWeight) {
        this.weight = boatWeight;
    }
    
    public double getPrice() {
        return this.price;
    }

    public void setPrice(double boatPrice) {
        this.price = boatPrice;
    }
    
    //COPY CONSTRUCTOR
    public Boat(Boat boat) {
        this.weight = boat.getWeight();
        this.price = boat.getPrice();
    }
    
    public String toString() {
        return "This boat weighs " + this.getWeight() + "kg and costs $" + this.getPrice() + ".";
    }
    
    public boolean equals(Boat boat) {
        if (!(boat instanceof Boat) || boat == null) {
            return false;
        } else if (this.price != boat.price || this.weight != boat.weight) {
            return false;
        } else {
            return true;
        }
    }
    
}

//Third class which extends Plane
package Heli;
import Plane.Plane;

public class Heli extends Plane{
    
    private int cylinders;
    private int year;
    private int capacity;
    
    public Heli() {
        cylinders = 6;
        year = 2018;
        capacity = 35;
    }

    public Heli(String planeBrand, double planePrice, int power, int cylinders, int year, int capacity) {
        super(planeBrand, planePrice, power);
        this.cylinders = cylinders;
        this.year = year;
        this.capacity = capacity;
    }

    public int getCylinders() {
        return this.cylinders;
    }
    
    public void setCylinders(int cylinders) {
        this.cylinders = cylinders;
    }
    
    public int getYear() {
        return this.year;
    }
    
    public void setYear(int year) {
        this.year = year;
    }
    
    public int getCapacity() {
        return this.capacity;
    }
    
    public void setCapacity(int capacity) {
        this.capacity = capacity;
    }
    
    //COPY CONSTRUCTOR
    public Helicopter(Helicopter helicopter) {
        super(helicopter);
        this.cylinders = helicopter.cylinders;
        this.year = helicopter.year;
        this.capacity = helicopter.capacity;
    }
    
    public String toString() {
        return "This heli is manufactured by " + super.getBrand() + " and costs $" + super.getPrice() + ". It has " + super.getPower() + " horsepower. It was manufactured in " + getYear() + ", has " + getCylinders() + " cylinders and has a total carrying capacity of " + getCapacity() + " lbs.";
    }

    public boolean equals(Heli heli) {
        if (!(heli instanceof Heli) || heli == null) {
            return false;
        } else if (this.cylinders != heli.getCylinders() || this.year != heli.getYear() || this.capacity != heli.getCapacity() || !(super.equals(heli))) {
            return false;
        } else {
            return true;
        }
    }
    
}

//Driver class where my copy takes place
public class Driver {


    private static Object[] newMixedArray = new Object[3];

    //THIS IS WHERE MY COPY ARRAY NEEDS TO BE IMPLEMENTED
    public static void copyObjects(Object[] newMixedArray) {
        Object[] copyArray = new Object[newMixedArray.length];
    
    }


    public static void main(String[] args) {
        
        newMixedArray[0] = new Plane("Bombardier", 50000000, 4000);
        newMixedArray[1] = new Boat("Boeing", 8500000.75, 8500);
        newMixedArray[2] = new Heli("Glastron", 250500.99, 837, 8, 2020, 35);
        

        copyObjects(newMixedArray);

    }

}

Now the kicker is that I cannot use clone() to create my copy array. At first, I created a simple loop to copy my original array into another array called "copyArray" and print out the values, however it came to my attention that this was simply a shallow copy and not a deep copy. I've been wracking my brain for the last several days trying to find a solution but have come up empty, especially since most answers I've found online don't seem to apply to situations with multiple classes.