I made I Plane and When I Press T I want the Speed to Gain +30 Speed ??

				function fly(m)	-- Main function that controls all of the flying stuff. Very messy.
					flying = true
					local pos,t = main.Position,time()
					local lastStall = false
					while ((flying) and (not dead)) do
						realSpeed = ((pos-main.Position).magnitude/(time()-t))	-- Calculate "real" speed
						pos,t = main.Position,time()
						local max = (maxSpeed+(-main.CFrame.lookVector.y*speedVary))	-- Speed variety based on the pitch of the aircraft
						desiredSpeed = (max*(on and throttle or 0))	-- Find speed based on throttle
						local change = (desiredSpeed > currentSpeed and 1 or -1)	-- Decide between accelerating or decelerating
						currentSpeed = (currentSpeed+(accel*change))	-- Calculate new speed
				--		local throttleNeeded = 
						local stallLine = ((stallSpeed/math.floor(currentSpeed+0.5))*(stallSpeed/max))
						stallLine = (stallLine > 1 and 1 or stallLine)
						panel.Throttle.Bar.StallLine.Position = UDim2.new(stallLine,0,0,0)
						panel.Throttle.Bar.StallLine.BackgroundColor3 = (stallLine > panel.Throttle.Bar.Amount.Size.X.Scale and Color3.new(1,0,0) or Color3.new(0,0,0))
						if (change == 1) then
							currentSpeed = (currentSpeed > desiredSpeed and desiredSpeed or currentSpeed)	-- Reduce "glitchy" speed
						else
							currentSpeed = (currentSpeed < desiredSpeed and desiredSpeed or currentSpeed)
						end
						local tax,stl = taxi(),stall()
						if ((lastStall) and (not stl) and (not tax)) then	-- Recovering from a stall:
							if ((realSpeed > -10000) and (realSpeed < 10000)) then
								currentSpeed = realSpeed
							else
								currentSpeed = (stallSpeed+1)
							end
						end
						lastStall = stl
						move.velocity = (main.CFrame.lookVector*currentSpeed)		-- Set speed to aircraft
						local bank = ((((m.ViewSizeX/2)-m.X)/(m.ViewSizeX/2))*maxBank)	-- My special equation to calculate the banking of the plane. It's pretty simple actually
						bank = (bank < -maxBank and -maxBank or bank > maxBank and maxBank or bank)
						if (tax) then
							if (currentSpeed < 2) then	-- Stop plane from moving/turning when idled on ground
								move.maxForce = Vector3.new(0,0,0)
								gyro.maxTorque = Vector3.new(0,0,0)
							else
								move.maxForce = Vector3.new(math.huge,0,math.huge)	-- Taxi
								gyro.maxTorque = Vector3.new(0,math.huge,0)
								gyro.cframe = CFrame.new(main.Position,m.Hit.p)
							end
						elseif (stl) then
							move.maxForce = Vector3.new(0,0,0)	-- Stall
							gyro.maxTorque = Vector3.new(math.huge,math.huge,math.huge)
							gyro.cframe = (m.Hit*CFrame.Angles(0,0,math.rad(bank)))
						else
							move.maxForce = Vector3.new(math.huge,math.huge,math.huge)	-- Fly
							gyro.maxTorque = Vector3.new(math.huge,math.huge,math.huge)
							gyro.cframe = (m.Hit*CFrame.Angles(0,0,math.rad(bank)))
						end
						if ((altRestrict) and (main.Position.y < altMin)) then	-- If you have altitude restrictions and are below the minimun altitude, then make the plane explode
							plane.AutoCrash.Value = true
						end
						updateGui(tax,stl)	-- Keep the pilot informed!
						main.Throttle.Value = throttle 
						wait()
					end
				end

Bind your function using the BindAction method of the ContextActionService. Also, don’t use ChurroRX’s method of KeyDown, as it is deprecated.

function yourcodehere()

end

game:GetService('ContextActionService'):BindAction(
    "CodeHere",
    yourcodehere,
    false,
    Enum.KeyCode.T
)