Plane moving down instead of forward?

My Plane is meant to move forward. It's working, but it's also moving down as well. This is the script I tried:

function Explode()
	local Lava = script.Parent.Parent.Parent.InnerPlane.Lava
	local num = 5
	Lava.Script.Disabled = false
	Lava.Transparency = 0
	repeat
		num = num+1
		Lava.Size = Vector3.new(num, num, num)
		wait(0.1)
	until num == 150
end

function ResetAll()
	game.Workspace.SelfDestructButton.ClickDetector.SelfDestructScript.Disabled = false
	game.ReplicatedStorage.SafeRoom.Parent = workspace
end

num = -2211
repeat
	num = num +1
	script.Parent.Position = Vector3.new(script.Parent.Position.X, script.Parent.Position.Y, num)
	wait(0.05)
until num == 2356
Explode()
wait(7.5)
ResetAll()
script.Parent.Parent.Parent:Destroy()

What happened? bit of help! Thanks!