Creating Realistic Plane Physics

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Creating realistic combat flight physics might seem challenging at first, but it’s defined by simple and abstract principles that are easier to implement than you might expect. After a few hundred hours of work, I created a flight physics model that takes ~1% of processing power each frame (assuming 60 fps). In this guide, I’ll walk you through the main ideas behind flight physics and give a practical example that you can use or adapt for your own projects.

The primary forces that effect the plane’s movement are thrust, drag, lift, and control surfaces(flaps, ailerons, rudder etc.).
Thrust, Drag, and Lift: These are straightforward linear forces represented with VectorForce objects.
Control Surfaces: Instead of simulating individual flaps, we use an AngularVelocity constraint to manage pitch, roll, and yaw to avoid performance overhead. With these forces ready, we can construct the flight model.

The flight model uses a “constructor” (Object Oriented Programming via Roblox tables) to create a plane object from custom-tuned performance values that developers can pass, allowing simulation of different plane types. We assume 1 stud = 1 meter and 1 Roblox Mass Unit (RMU) = 1 kg. To give the illusion of more map space, the plane is scaled down by 10x, meaning proportional changes:

  • Mass is reduced by 10^3.
  • Force strengths are divided by 10^3.
  • Gravity is scaled down by 10(because of distance).
  • Speed and altitude are multiplied by 10 to maintain the illusion and for consistent measurements

For the best performance, the flight physics is run on the client. However, to allow the client to manage the physics of the plane mesh, we need to give it NetworkOwnership. An important thing to note is that we need somewhere to store the custom plane performance profile tables and pass them to the flight model, so we store them in the server script storage, and pass them to the client along with ownership of the plane mesh. The client uses a request manager module script with remote events as children to communicate with the server:

-- Request manager script
local RequestManager = {}

local RequestOwnership = script.RequestOwnership
local OwnershipStatus  = script.OwnershipStatus
local RequestProfile   = script.RequestProfile
local ProfileStatus    = script.ProfileStatus

-- Request network ownership
function RequestManager:requestOwnership(plane)
	RequestOwnership:FireServer(plane)
	OwnershipStatus.OnClientEvent:Connect(function(pass) print(pass and "Ownership set" or "Failed to set ownership")end)
end

function RequestManager:requestProfile(plane)
	local profile
	local profileReceived = Instance.new("BindableEvent")
	RequestProfile:FireServer(plane) -- Fire server request

	-- Handle profile response
	local function handleProfileResponse(success, receivedProfile)
		if success then
			profile = receivedProfile
			print("Profile received")
		else
			print("Failed to get profile")
		end
		profileReceived:Fire() -- Notify that data is ready
	end
	
	-- Connect the handler & wait for the profile to be received
	ProfileStatus.OnClientEvent:Connect(handleProfileResponse) 
	profileReceived.Event:Wait() 

	return profile
end

return RequestManager

On the server’s side, we have two normal scripts to communicate with the client:

-- Ownership script
local Players = game:GetService("Players")
local RS = game:GetService("ReplicatedStorage")
local RequestManager   = RS:WaitForChild("RequestManager")
local OwnershipRequest = RequestManager:WaitForChild("RequestOwnership")
local OwnershipStatus  = RequestManager:WaitForChild("OwnershipStatus")


local function setNetworkOwnership(player, plane)
	if not plane or not player then return false end
	local pass, message = pcall(function() plane:SetNetworkOwner(player) end)	    -- Set network ownership
	return pass or (warn("Failed to set network ownership: " .. message) and false) -- Return success or failure
end

-- Handle ownership requests from clients and return whether ownership has been given
OwnershipRequest.OnServerEvent:Connect(function(player, plane) OwnershipStatus:FireClient(player, setNetworkOwnership(player, plane)) end)

----------------------------------------
-- Plane performance profiles script
local profiles = require(script.PlaneProfiles)
local RS = game:GetService("ReplicatedStorage")
local RequestManager = RS:WaitForChild("RequestManager")
local profileRequest = RequestManager:WaitForChild("RequestProfile")
local profileStatus  = RequestManager:WaitForChild("ProfileStatus")

local function handleProfileRequest(player, plane)
	local profile = profiles[plane]  				    -- Get profile using the plane
	local success = profile ~= nil  					-- Check if profile exists
	profileStatus:FireClient(player, success, profile)  -- Fire client with result
end

profileRequest.OnServerEvent:Connect(handleProfileRequest)

Once the client has control over the plane model, we can finally apply our physics.

Variables track the plane’s local frame of reference, and the ApplyPhysics function executes three steps each frame via BindToRenderStep:
Handle Controls: Processes player inputs for pitch, roll, yaw, and throttle.
Update Physics: Calculates and applies forces like thrust, drag, and lift.
Update Camera and HUD: Updates the camera and the HUD with flight data.

function Plane:ApplyPhysics()
	local function handleControls(deltaTime)
		Controls.handleControls(self.flightControl, self.plane, self.stats, self.Gun, velocity, deltaTime)
	end
	local function UpdateState(deltaTime)
		self:updateLocalVariables()
		self:UpdateForces(deltaTime)
	end
	local function UpdateCamera(deltaTime)
		PCS.updateCamera(camera, self.plane) -- Update the camera(Handles its own controls)
		HUDManager.UpdateHUD(velocity, altitude, AOA, Controls.getThrottle()) -- Display info to the HUD
	end

	-- Adding 1 to update the camera after roblox's internal cam updates but before it renders(for our own plane camera)
	RService:BindToRenderStep("HandleInputs", Enum.RenderPriority.First.Value, handleControls)    -- #1 Handle controls
	RService:BindToRenderStep("UpdatePhysics", Enum.RenderPriority.First.Value + 1, UpdateState)  -- #2 Handle physics updates
	RService:BindToRenderStep("UpdateCamera", Enum.RenderPriority.Camera.Value + 1, UpdateCamera) -- #3 Handle plane cam and HUD
end

The second bind calls the UpdateForces function, which calculates the strength and direction of our forces:

function Plane:UpdateForces(deltaTime)
	if velocity.Magnitude == 0 then velocity = Vector3.new(0,0,0.001) end -- To avoid NaN calculations
	
	-- Calculate forces
	local thrust = Physics.calculateThrust(self.stats.Thrust, Controls.getThrottle())
	local drag   = Physics.calculateDrag(velocity, self.stats.DragPower, altitude) * ABM * GM
	local lift   = Physics.calculateLift(velocity, self.stats.LiftPower, AOA)

	Physics.alignVV(self.plane.AssemblyLinearVelocity, CF.LookVector, Controls.getThrottle(), self.plane, deltaTime)

	-- Apply the forces
	self.thrust.Force  = thrust * CF.LookVector  -- Thrust is applied towards the lookvector/nose
	self.lift.Force    = lift   * CF.UpVector    -- Lift is perpendicular to the wings and towards the up vector
	self.drag.Force    = drag   * -velocity.Unit -- The Drag force is opposite to Velocity
	
	HUDManager.UpdateHUD(velocity, drag, altitude, AOA, CF)
end

Using the plane’s AoA, which is the angle between the plane’s nose (look vector) and its velocity vector on the pitch axis, we can calculate our forces(Equations are simplified for performance):

function Physics.calculateThrust(Thrust, Throttle, altitude, maxAltitude)
	local altitudeFactor = math.exp(-altitude/maxAltitude) -- Engine performance degrades with altitude
	
	-- Thrust is derived by multiplying the max thrust by the throttle, with respect to the plane's altitude
	return (Thrust/1000) * Throttle * altitudeFactor
end

function Physics.calculateLift(velocity, liftPower,  AOA)
	-- Lift = 0.5 * velocity^2 * liftcoefficient * liftpower(hand tuned)
	-- A curve sin(3x) derives the Lift Coefficient outputting values from 1 to -1 depending on the AOA.
	-- Only values from -60 to 60 aoa will output coefficiencients from -1 to 1 beyond is the stall region, where coefficient stays 0
	local liftCoefficient = math.clamp(math.sin(math.rad(3 * AOA)), -60, 60)
	local lift = 0.5 * velocity.Magnitude^2 * liftCoefficient * liftPower
	
	return lift/1000 
end

function Physics.calculateDrag(velocity, dragPower, altitude)
	if velocity.Magnitude == 0 then return Vector3.zero end -- Dont return NaN drag

	-- Drag = 0.5 * velocity^2 * airdensity * dragCoefficient 
	-- Airbrakes and gears are added to the final drag force as extra drag values
	local dragCoefficient = dragPower * velocity.Magnitude
	local airDensity = 1.2 * math.exp(-altitude / 25000) -- Simplified exponential decay
	local dragForce = 0.5 * velocity.Magnitude^2 * airDensity * dragCoefficient

	return dragForce/1000
end

The rest is simple. We use a controls module that accepts inputs from the user to roll, pitch and yaw the plane. We degrade the strength of the inputs based on the plane’s speed to mimic the loss of control with loss of speed that planes in real life experience. Additionally, we can simulate post stall physics behavior when the plane drops below critical speed. Completely realistic stall behavior is not computationally feasible, so we compromise. What we do is find the direction of the shortest angle in the down direction, and pull the plane’s nose down towards that direction. We account for the plane’s roll, pitching up when its upsidedown, and pitching down when its right side up:

function Physics.handleStall(speed, stallSpeed, planeCFrame, baseAngularVelocity, pitchAngle)
	-- Check stall condition: at or below stall speed and significant pitch angle
	if speed <= stallSpeed and math.abs(pitchAngle) > 0 then
		local stallFactor = math.clamp((stallSpeed - speed)/stallSpeed, 0, 1) -- Stall factor (0-1) based on how much we are below stallSpeed
		local pitchDirection = math.sign(planeCFrame.UpVector.Y) -- Determine pitch direction (using the plane's UpVector)
		local angleError = math.abs(pitchAngle) -- Calculate the error in pitch (how far we are from level)

		-- Calculate a torque factor based on the pitch error (linear scaling)
		local torqueFactor = angleError * 2
		local minTorqueFactor = 0.05
		torqueFactor = math.max(torqueFactor, minTorqueFactor)

		-- Calculate the base pitch correction (in radians)
		local pitchCorrection = math.rad(1) * pitchDirection * torqueFactor

		-- Instead of applying the full correction, blend between the control input and the correction value so 
        -- This way the player can has at least some control to recover
		local controlPitchVelocity = baseAngularVelocity.X
		local targetPitchVelocity = controlPitchVelocity - pitchCorrection
		local blendedPitchVelocity = math.lerp(controlPitchVelocity, targetPitchVelocity, stallFactor)

		return Vector3.new(blendedPitchVelocity, baseAngularVelocity.Y, baseAngularVelocity.Z) -- Return with pitch correction
	end
	
	return baseAngularVelocity -- If not stalling, just return the base angular velocity
end

Flight computer behavior can usually be added here to simulate things like G and AOA limiters. The way we limit the AOA or Gs the plane can utilize by decreasing input authority when approaching these limits. In my flight model, I only use an AOALimit variable to set the maximum angle of attack the plane can utilize(passed in the performance profile table), then gradually decrease pitch input authority as the AOA approaches its limit. In the end, this is the complete controls module script:

local Controls = {}
local UIS     = game:GetService("UserInputService")
local Physics = require(script.Parent.Physics)
local FCS     = script.Parent.FireControlSystem
local Gun     = require(FCS.Gun)

-- State variables
local airbrakes = false
local gears     = true
local GForce    = 0
local throttle  = 0

local CD = {
	T = 0,
	G = 0,
}

-- Handle all inputs
function Controls.handleControls(flightControl, plane, stats, gun, velocity, AOA, deltaTime)
	local pitchR, rollR, yawR = plane.CFrame:toEulerAnglesYXZ()
	local pitch = math.clamp(math.deg(pitchR), -90, 90)
	local yaw   = math.deg(yawR)
	local roll  = math.deg(rollR)

	local rollInput  = 0
	local pitchInput = 0
	local yawInput   = 0
	local axisGLimit = stats.AxisGLimit

	local degToRad = math.pi/180
	GForce = Physics.calculateGForce(plane.AssemblyAngularVelocity, velocity, plane.CFrame)

	-- Process control inputs
	if UIS:IsKeyDown(Enum.KeyCode.LeftShift)   then throttle = math.min(throttle + 0.0025, 1) end
	if UIS:IsKeyDown(Enum.KeyCode.LeftControl) then throttle = math.max(throttle - 0.0025, 0) end
	if UIS:IsKeyDown(Enum.KeyCode.W) then pitchInput = -stats.TurnRate * 0.5 end
	if UIS:IsKeyDown(Enum.KeyCode.S) then pitchInput = stats.TurnRate  end 
	if UIS:IsKeyDown(Enum.KeyCode.A) then rollInput  = stats.RollRate  end
	if UIS:IsKeyDown(Enum.KeyCode.D) then rollInput  = -stats.RollRate end
	if UIS:IsKeyDown(Enum.KeyCode.Q) then yawInput   = stats.YawRate   end
	if UIS:IsKeyDown(Enum.KeyCode.E) then yawInput   = -stats.YawRate  end
	if UIS:IsMouseButtonPressed(Enum.UserInputType.MouseButton1) then Gun.handleGunFiring(plane, gun, velocity, true, deltaTime) end
	
	local controlAuthority = Physics.DegradeControl(velocity.Magnitude * 3.6, stats.OptimalSpeed, stats.MaxSpeed)

	-- Degradation control on each axis
	pitchInput = pitchInput * controlAuthority
	rollInput  = rollInput  * controlAuthority
	yawInput   = yawInput   * controlAuthority

	pitchInput = Controls.AOALimiter(pitchInput, AOA, stats.AOALimit) -- Limit the plane's max AOA
	rollInput = rollInput + (yawInput * 1.75) -- Roll when the plane yaws
	local baseAngularVelocity = Vector3.new(pitchInput * degToRad, yawInput * degToRad, rollInput * degToRad) -- Calculate base angular vel

	-- Apply stall effect to the base angular velocity
	local finalAngularVelocity = Physics.handleStall(velocity.Magnitude * 3.6, stats.StallSpeed, plane.CFrame, baseAngularVelocity, pitch)

	flightControl.AngularVelocity = finalAngularVelocity
end

function Controls.AOALimiter(pitchInput, AOA, maxAOA)
	local aoaPercentage = math.abs(AOA)/maxAOA 	-- Get absolute AOA and normalize it relative to max

	-- For nose down input when AOA is already negative/pos, allow recovery
	if (pitchInput < 0 and AOA < 0) or (pitchInput > 0 and AOA > 0) then
		if aoaPercentage >= 1 then return 0 end -- If we are beyond max AOA, prevent further increase

		-- Start reduction at 70% of max AOA
		if aoaPercentage > 0.7 then
			local normalizedProgress = (aoaPercentage - 0.7) / 0.3
			local reductionFactor = normalizedProgress^2
			return pitchInput * (1 - reductionFactor)
		end
	end
	
	return pitchInput
end

function Controls.handleUtilControls(deltaTime)
	for key, cooldown in pairs(CD) do CD[key] = math.max(cooldown - deltaTime, 0) end -- Update cooldowns
	if UIS:IsKeyDown(Enum.KeyCode.T) and CD["T"] <= 0 then 
		CD["T"] = 4	
		airbrakes = not airbrakes
		print("Airbrakes activated")
	end
	if UIS:IsKeyDown(Enum.KeyCode.G) and CD["G"] <= 0 then 
		CD["G"] = 3
		gears = not gears 
		print("Gears activated")
	end
end

function Controls.getGears()     return gears     end
function Controls.getAirbrakes() return airbrakes end
function Controls.getThrottle()  return throttle  end
function Controls.getGForce()    return GForce    end

return Controls

With just a few hundred lines of code, we have already created the majority of the behavior that composes our flight model. Finally, we implement a plane camera system to follow the plane around and allow the player to control. Essentially what happens is the camera will follow the plane around and allow the player to rotate it about its pitch/yaw axes by holding v. Once the player lets go of the v key(freelook key), the camera will start snapping back to the default view angle that it follows the plane around with. Here is the implemented behavior:

local PCS = {}
local CUIS = game:GetService("UserInputService")
local CAMERA_DISTANCE                = 2.5    -- Distance behind plane in studs
local DEFAULT_YAW, DEFAULT_PITCH     = 0, -20 -- Default view angle relative to plane
local PITCH_INCREMENT, YAW_INCREMENT = 5, 5   -- Increment in angle at which it steps back to the default viewing angle

-- Initialize tracking variables to DEFAULT values 
local currentYaw, currentPitch = DEFAULT_YAW, DEFAULT_PITCH
local snappingBack = false
local isFreeLook = false

local function snapToDefault()
	-- Update and track the current angles during snap-back
	currentPitch = currentPitch > DEFAULT_PITCH and 
		math.max(currentPitch - PITCH_INCREMENT, DEFAULT_PITCH) or 
		math.min(currentPitch + PITCH_INCREMENT, DEFAULT_PITCH)

	local defaultYawWithOffset = DEFAULT_YAW + 360 * math.floor((currentYaw - DEFAULT_YAW) / 360 + 0.5)
	currentYaw = currentYaw > defaultYawWithOffset and 
		math.max(currentYaw - YAW_INCREMENT, defaultYawWithOffset) or 
		math.min(currentYaw + YAW_INCREMENT, defaultYawWithOffset)
end

function PCS.updateCamera(camera, body)
	camera.CameraType = Enum.CameraType.Scriptable
	CUIS.MouseIconEnabled = false
	CUIS.MouseBehavior = Enum.MouseBehavior.LockCenter

	local planePos = body.CFrame.Position
	local planePitch, planeYaw, _ = body.CFrame:ToOrientation()

	if CUIS:IsKeyDown(Enum.KeyCode.V) then
		if not isFreeLook then
			-- Convert from local to world angles when entering freelook
			currentYaw = math.deg(planeYaw) + currentYaw
			currentPitch = math.deg(planePitch) + currentPitch
			isFreeLook = true
			snappingBack = false
		end

		local delta = CUIS:GetMouseDelta()
		if delta.Magnitude > 0 then
			currentYaw = currentYaw - (delta.X * 0.1)
			currentPitch = math.clamp(currentPitch - (delta.Y * 0.1), -90, 90)
		end
	else
		if isFreeLook then
			-- Convert from world to local angles when exiting freelook
			currentYaw = currentYaw - math.deg(planeYaw)
			currentPitch = currentPitch - math.deg(planePitch)
			isFreeLook = false
			snappingBack = true
		end

		if snappingBack then
			snapToDefault()
		end
	end

	local rotation
	if isFreeLook then
		-- In freelook, use world space orientation
		rotation = CFrame.fromOrientation(math.rad(currentPitch), math.rad(currentYaw), 0)
	else
		-- When not in freelook, make it relative to plane
		rotation = CFrame.fromOrientation( planePitch + math.rad(currentPitch), planeYaw + math.rad(currentYaw), 0)
	end

	local targetCFrame = CFrame.new(planePos) * rotation
	local cameraPos = planePos - targetCFrame.LookVector * CAMERA_DISTANCE
	camera.CFrame = CFrame.new(cameraPos, planePos)
end

return PCS

If you made it this far, and your interested in using this, ill make a new post soon where I explain how to create your own plane profiles and work with this implementation. Here is an example:
CombatFlightPhysics.rbxl (346.5 KB)

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